COMPUTERIZED RESEARCH SYSTEM AND METHODS FOR PROCESSING AND DISPLAYING SCIENTIFIC, TECHNICAL, ACADEMIC, AND PROFESSIONAL INFORMATION

Abstract: The present invention is a research tool consisting of a computerized system and method for processing and displaying information. The system can be applied to the content of any scientific, technical, academic, or professional publishing sub-discipline in which each content item can be classified under a collection of principles ("classification categories") of the discipline, for example: law (6), immigration law (29), science, polymer chemistry, medicine, and economics (7). The present invention employs as appropriate for the sub-discipline, the traditional content and system tools of computerized research systems: file-building software, file-processing software (30), including full-text searching and hypertext links (11), a user interface, and content types such as tables of contents, index terms, abstracts, journal articles (7), parts and subparts of books, research notes, and reports, drawings, cases (6), statutes, and the like. The content of the computerized system records the knowledge and research of the sub-discipline. Each classification category is an expression of an authoritative definition, principle, or relevant fact in the sub-discipline.

Description: COMPUTERIZED RESEARCH SYSTEM AND METHODS FOR PROCESSING AND DISPLAYING SCIENTIFIC, TECHNICAL, ACADEMIC, AND PROFESSIONAL INFORMATION A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent disclosure, as it appears in the Patent and Trademark Office public patent files or records, but otherwise reserves all copyright rights whatsoever. I. BACKGROUND OF THE INVENTION A. Field of the Invention The present invention is a computerized system for processing and displaying information that can be applied to many of the scientific, technical, academic, and professional publishing disciplines, for example, chemistry, medicine, economics, and law, that have multiple types of content that can be classified under a collection of principles of the discipline. While, the functions and features of the present invention will be described herein in the context of legal publishing and research, the present invention is not so limited. B. Description of Related Art A wide variety of computerized systems for processing, searching, retrieving, and displaying textual information have been proposed and implemented in the past forty years in diverse subject-matter areas (the law, medicine, military intelligence) and in different implementation environments (single-site computer systems, the World Wide Web) . Additionally, there are many software products running on computer systems that help legal practitioners create work product and manage their practices, such as document-assembly systems, case-management tools, and time and billing systems. An individual performing legal research will look through the legal information or "legal content" available to him/her. More often than not the researcher will use various indexes or other research aids and/or methods to focus his/her research. In accordance with the present invention, legal information is classified by type, namely, primary source or secondary source, referred to herein collectively as "research materials." Further in accordance with the present invention, the various different methods and/or aids the researcher employs to find the relevant legal information are referred to herein as "finding tools." (1) Research materials (a) Primary sources Primary sources comprise original print or electronic materials created by public organizations such as the judicial, legislative, and executive branches of the federal and state governments, and published by either public or private organizations. Among some of the most important types of primary sources are: constitutions and treaties, court decisions and rules, legislative codes and history, and administrative and executive materials (e.g., regulations, decisions, orders, rules and procedures, notices, reports, arbitrations, advisory, and executive orders). A fairly exhaustive collection of types of primary sources may be found in the standard reference work for primary source citations, "The Bluebook, A Uniform System of Citation," published by the Harvard Law Review Association. (b) Secondary sources Secondary sources comprise print or electronic materials created primarily by private legal publishers to help the user analyze primary sources. Legal publishers, bar associations, and educational institutions offer numerous secondary sources of various sizes and types, for example: treatises and encyclopedias, form books and practice guides, hornbooks and restatements, current looseleaf services and newsletters, legal newspapers, case digests, annotated codes, and law reviews . The categories of secondary sources listed above are informal, intended only to provide a shorthand way of describing the predominant feature of a given publication. In fact, many titles are published m combined form and could be listed under multiple secondary-source categories, as well as under finding tools described below. For example, "treatises" (e.g., "Collier on Bankruptcy") often include a substantial number of forms, and are updated by newsletter as well as through conventional supplementation, while the footnotes m the treatises, by virtue of their brief case annotations and value in locating relevant primary sources, are somewhat analogous to case digests. The distinction is made here between secondary sources and finding tools primarily to help explain the functionality of the present invention. For example, annotated codes are a combination of classification by code section, the text of the code sections, case citations, and case annotations (respectively, finding tool, primary source, finding tool, and secondary source) . In fact, many publications that explain the mechanics of legal research simply group within the secondary- source category any material that is not primary source. In addition, some secondary-source titles (particularly the current looseleaf services) also serve as "unofficial" primary-source reporters. (2) Finding tools As noted earlier, finding tools comprise print or electronic materials or computer-assisted techniques that help the user find research materials. Examples of finding tools, more fully described below, are: full-text searching, cross- references, specialized primary-source finding tools, tables of contents, indexes, and tables of primary-source authorities. Such categories are informal, provided only to facilitate review. As the examples below make clear, some research materials and some finding tools are published in combined form; thus, components of some finding tools could be considered analytical in nature, and thus included under one of the secondary-source categories described above. Full text searching is usually offered as an integrated component of electronic primary- or secondary-source publications made available on-line, on CD-ROM or otherwise. Cross-references comprise page numbers and case citations (m research materials and finding tools) to another location m the same publication or to a location in another publication; in electronic publications, such cross-references may be implemented as hypertext links. Specialized primary-source finding tools, such as citators and legal taxonomies, are sometimes combined with research materials. Citators identify subsequent cases (or administrative decisions) that have referred to ("cited") a particular case or code section or administrative decision. Taxonomies of the law, of which one of the best known is the West® Key Number System, combine a classification scheme with case digests, which are a combination of: subject-matter classifications, case citations, and case annotations (respectively, finding tool, finding tool, and secondary source) . Tables of contents provide hierarchies and text locations (chapter numbers, section numbers, page numbers, and the like) for a particular publication. Indexes provide alphabetically ordered words and phrases denoting the location of principles, concepts, or legally relevant facts in a particular research-material publication or finding-tool publication. Tables of primary-source authorities designate the location within a publication where a particular type of primary source (e.g., case or code section or form) is discussed. C. Difficulties with Prior Methods The research materials and finding tools currently published, whether in print or electronic form, including those discussed above, have serious drawbacks that contribute to the time-consuming and frequently incomplete nature of research. Again, even though the details set forth below focus on legal publishing and research, in many cases similar concerns exist for other types of prior professional, technical and reference research methods and systems. (1) Research material drawbacks A given publication intended for legal research generally offers one class of research material in one linear sequence in one classification scheme. Cross-references may be incomplete and updating is limited. The limitation to one class of research material was historically dictated by the space constraints of printed books. No single publication includes the text of all the research materials even for one legal-practice area. Where electronic publications do offer various research materials, it is more in the nature of separate publications that have simply been packaged together than as a fully integrated whole . The limitation of one linear sequence was dictated by the static, linear nature of printed books. Whenever any research materials are consulted, they must always be read in the order in which they were written. Finding tools such as tables of contents, indices, full-text searching, and hypertext links make it possible to move to different locations within publications, but not to reorder the research material in any way - i.e., once relevant material is found, it must be read in its original sequence. For example, if a case raises four issues, the analysis of those issues is unlikely to be contiguous in any secondary source; in a treatise, for example, the lawyer must find each of them separately, skipping over generally irrelevant intervening material. The limitation of one classification scheme is similar to the limitation of one linear sequence. The user is bound to the table-of-contents hierarchy under which the research materials were written. For example, if the analysis in a bankruptcy treatise is published in order by the concepts of bankruptcy (as in "Norton on Bankruptcy"), that is the only order in which the book can be read; if a lawyer wants to read similar analysis arranged in a table-of-contents hierarchy based on the bankruptcy rules, he/she must turn to another publication (e.g., "Collier on Bankruptcy"). Currently, virtually every electronic publication is derived from and constrained by this model of print publishing. Even electronic publications that have no exact correspondent in print (such as Lexis® and Westlaw® electronic publications) mimic the organization of printed case and code reporters (with the important addition of full-text finding tools). Some electronic publications do provide limited options for sorting the research material of a file by some of its attributes. For example, in Westlaw, cases satisfying the computer search may be sorted by reporter volume and page, date of decision, and statistically determined relevancy. But the cases cannot be put into other, potentially much more useful hierarchies, for example, by code section or regulatory section discussed in the cases, or by the headings in a treatise table of contents. Cross-references are woefully incomplete. In the prior methods, cross-references between research materials must be manually assigned, one by one, by the author (e.g., a judge writing a case, or his clerk), or a legal editor. No prior-art publisher has offered relatively complete cross-references (i.e., imbedding in relatively all items of research material that are relevant to a specific legal issue cross-references [or links] to relatively all other items of research material that are relevant to the same legal issue), so that no matter what item of research material the user happens upon first, relatively all relevant material would be instantaneously available to him or her. The problem in the prior methods is obvious when the manual linking effort required is stated in quantitative terms: for example, to link just 10 items (such as 4 cases, 3 code sections, 2 cases, and 1 form) in an electronic product would require the manual assignment of 45 one-way links (the computer and software will automatically build the return links) according to the following formula, where n equals the total number of items of research materials: n*(n-l)/2. The number of required one-way links increases geometrically, as follows : 20 items require 190 links 30 items require 435 links 40 items require 780 links 50 items require 1,225 links 100 items require 4,950 links 250 items require 31,125 links 500 items require 124,750 links. With limited linking of relevant research materials the norm in the prior methods, the researching lawyer cannot be sure that the cross-references in one or even several items of relevant research material that he/she has found will point to all other relevant research material. Other potentially relevant research material can only be found through time- consuming additional research more often than not in different print or computer publications. Even though (with the advent of on-line full-text systems) most primary sources are updated daily, secondary- source publications (with the exception of small newsletters), whether in print or on line, are only updated several times a year. This disparity in relative timeliness is attributable to several factors: First, there is the sheer number of secondary-source publications that need to be updated, as described above. Second, because each publication must be maintained as an independent entity, a new case annotation, for example, must be inserted into every relevant publication (treatise, practice guide, desk edition, form set, and the like) in a separate manual process; moreover, the linear sequence of the publication often creates fragmentation of coverage such that the same or related legal issues are discussed at different parts of the same publication, and the incomplete nature of cross-references makes such potential locations for the new case annotation hard for the editors to find. Third, existing cross-references and finding tools like tables of contents, indices, and tables of cases and code sections may have to be changed to reflect added and deleted materials . For users who prefer or need to use secondary sources, the significant mismatch in timeliness between primary and secondary sources means that even after the relevant law has been found with the secondary sources, the separate up-to-date primary sources, with their own peculiar finding tools, must be checked to ensure that the law as found m the secondary sources is still accurate. Constrained by this space-limited, static model, but recognizing that different problems and different levels of user expertise require different approaches to research, legal publishers have developed multiple types of publications in most every major area of practice (intellectual property, securities, tax, and more than a dozen others), of the sort described above as primary sources, secondary sources, and finding tools. Although these publications overlap substantially in coverage, the content still differs m important respects of comprehensiveness, organization, and timeliness. As a consequence, to see the text of different kinds of research materials and to reduce the chance that he/she has missed something, the researching lawyer must almost always undertake the time-consuming task of consulting several different print or electronic publications, each with its own sequence, classification scheme, numbers of cross- references, and currency of information. (2) Finding tool drawbacks Some finding tool drawbacks include missing relevant research materials, restrictions to a single type of research material or problems integrating different research materials. First, because of the complexity of legal materials, the differences in the interpretation that different humans put on the same words, and the vagaries of the English language, no finding tool, not even computer-based full-text searching, is absolutely perfect. All can miss research materials that may be relevant to the lawyer's specific research problem, and all can produce false drops (irrelevant materials that the lawyer must review and discard) . To minimize missing relevant research materials, the careful lawyer will employ multiple finding tools, a time-consuming process. Second, many finding tools are restricted m scope to a single type of research material. For example, West's® Key Number System can be used to find case law, but not administrative decisions, code sections, or regulation sections (except to the extent that hypertext links m cases and West® case digests point to such materials) . Since typically many research materials bear on a legal problem, the lawyer must consult several finding tools, often based on different principles. Third, even general-purpose finding tools (such as full- text searching) not restricted to a single type of research material do not integrate different research materials related to the same point of law. For example, in some publishers' CD- ROM services, a full-text search can generally be run against all primary- and secondary-source publications which that publisher makes available in a given practice area. A full- text search in a typical publisher's CD-ROM might return 23 hits (e.g., 10 cases, 4 code sections, 6 regulations, and 3 official forms) . Because the linkages among these materials are incomplete, the system can generally only display each kind of material in the sequence in which it appeared in the publication, with materials from each different publication shown separately in the sequence of that publication. The system cannot show the different kinds of materials in relation to each other (e.g., which of the 4 code sections, 6 regulations, 3 official forms, and remaining 9 cases relate to the first issue discussed in the second case retrieved) . II. SUMMARY OF THE INVENTION The present invention is a computerized research method and system for processing and displaying information which provides for generally less time consuming and more complete research than heretofore provided. The present invention can be applied to many scientific, technical, academic, and professional publishing disciplines - for example, chemistry, medicine, economics, and law - that have multiple types of content that can be classified under a collection of principles (referred to herein as "classification categories") of the discipline. Moreover, through the direct and indirect linking of such a collection of classification categories and content in a service developed using the teachings of the present invention, research can be completed more quickly, thoroughly, and accurately than is possible using current products. Such a service provides, in a single product, all the comprehensiveness, integration, currency, and variations in display of (sub) discipline content that can only be accomplished with dozens of current research products. The system of the present invention divides the content of each discipline (e.g., chemistry or law) or subdiscipline (e.g., polymer chemistry or immigration) into three general components - classification categories, source items, and finding tools. Each such classification category comprises an expression of an authoritative definition, principle, or relevant fact in the (sub) discipline . Taken as a whole, such classification categories comprise a coherent body of relevant authoritative definitions, principles, or facts in the (sub) discipline . In the discipline of law, three preferred forms of a collection of classification categories (the first two of which are described in detail below) are a collection of narrow black- letter statement identifiers, a collection of West® Key Number Headings, and a collection of treatise table-of-contents entries. Source items record the authoritative knowledge and research of a scientific, technical, academic, or professional (sub) discipline and comprise: journal articles, parts and subparts of books and encyclopedias, letters to the editor, research notes and reports, drawings, symposia proceedings, memoranda, legislative documents, judicial decisions, statutes, and regulations. Each source item has a source-item identifier, which comprises a short, descriptive heading for the source item and is the conventional means by which the item is denoted in the literature of a (sub) discipline . In the discipline of law, in accordance with preferred embodiments of the present invention, source items are generally categorized as primary-source items or secondary-source items (and their respective identifiers). Finding tools help the user find source items and comprise: (sub) discipline names, index terms, table-of- contents entries, and tables of source-item identifiers. (Sub) discipline names comprise commonly used descriptive designations for the major areas into which the scientific, technical, academic, or professional practice is customarily divided. Index terms comprise one or more words designating principles, concepts, or facts relevant to the scientific, technical, academic, or professional (sub) discipline . Table- of-contents entries comprise classification categories of the (sub) discipline with table-of-contents positions in which the classification categories serve as table-of-contents entries. Tables of source-item identifiers comprise an ordered list of source items, typically of a single type. Finding tools used in the discipline of law are described in detail below. The present invention utilizes the above base of (sub) discipline content together with its file-building system, file structures, file-processing system, and file- processing-system user interface to provide for a research system that overcomes many of the problems associated with prior methods and systems. Classification categories are linked to source items and to finding tools. The functionality of the present invention is derived from the breadth and precision of its collection of classification categories and the extent of the computer- based, bi-directional direct links between each classification category and related source items and finding tools . Such links enable direct and indirect linking between related source items and finding tools, and thereby fundamentally transform the way in which traditional information content of a scientific, technical, academic, and professional discipline can be found and displayed. A preferred embodiment of the present invention that employs a collection of classification categories designed and written specifically for the invention (e.g., "narrow black-letter statement identifiers") will deliver a higher level of functionality than an embodiment employing a collection of classification categories derived merely from current legal-research products (e.g., West® Key Number Headings or treatise tables of contents) . Although preferred embodiments of the present invention are described below in detail with respect to legal-research methods and systems, it is desired to emphasize that this is for the purpose of illustrating and describing the invention, and should not be considered as necessarily limiting the invention, it being understood that many modifications can be made by those skilled in the art while still practicing the invention claimed herein. III. BRIEF DESCRIPTIONS OF THE DRAWINGS Figures are identified by whole numbers, followed, where appropriate, by a reference to the particular preferred embodiment of the present invention being illustrated: " [B] " for the preferred embodiment using a collection of narrow black-letter statement identifiers as the collection of classification categories, and " [W] " for the alternative preferred embodiment using a collection of West® Key Number Headings - e.g., FIG. 3[B] and FIG. 22 [W] , respectively. Where neither " [B] " nor " [W] " appear, the figure applies to both preferred embodiments unless otherwise indicated. FIG. 1 is a block diagram of system components for one embodiment of the invention directed to any professional, technical or reference publishing discipline. FIGS. 2, 3[B], and 4 [W] are block diagrams of system components for the present invention in the discipline of law. FIGS. 5[B]-8[B] show authoring steps in this preferred embodiment of the present invention. FIGS. 9[B]-10[B] show the layout of the HTML record template used in FIGS. 5[B]-8[B]. FIG. 11 shows a partial layout of the full-text serial file. FIG. 12 shows the form of inverted-index entries for full-text searching. FIG. 13 shows the index-table entry linking the citation of a case or its short name to the location of the case in the full-text serial file. FIG. 14 shows an entry from an index for hypertext links. FIG. 15 is a diagram showing the conceptual links in the discipline of law, in any embodiment of the present invention. FIGS. 16 [B] and 17 [W] are diagrams showing the links between legal content. FIGS. 18-20 show direct and indirect linking of content. FIGS. 21 [B] and 22 [W] show the inter-relationships among files. FIGS. 23 [B] and 26 [W] show the computer and software- system steps employed by the file-building system to create on-line files in the first primary file structure from primary-source files. FIGS. 24 [B] and 27 [W] show the computer and software- system steps employed by the file-building system to create on-line files in the first primary file structure from secondary-source and finding-tool files. FIGS. 25 [B] and 28 [W] show the computer and software- system steps employed by the file-building system to create on-line files in the secondary primary file structure from secondary-source and finding-tool files. FIGS. 29-34 are flowcharts showing the interrelationships among screen displays. FIGS. 29-30 show embodiments of the present invention using any collection of classification categories; FIGS. 31[B]-32[B] show one preferred narrow black-letter statement identifier embodiment; and FIGS. 33 [W] -34 [W] show one preferred West® Key Number Heading embodiment . FIGS. 35-142, further described below, are screen displays for the sample user interface (i.e., a graphical user interface) in two preferred embodiments of the present invention. Such Figures are identified by whole numbers, followed in each instance by two references: first, a designation as to whether the display is of a " [B] " or " [W] " embodiment, and second, a designation as to which type of general research activity (denoted as one of 16 GUI PATTERNS) the Figure represents. For example, the reference "FIG. 78 [B- 8]" signifies that FIG. 78 illustrates a research activity within GUI PATTERN 8 for the preferred embodiment using a collection of narrow black-letter statement identifiers as the collection of classification categories. The reference FIG. 111[W-12] signifies that FIG. Ill illustrates a research activity within GUI PATTERN 12 for the alternative preferred embodiment using a collection of West® Key Number Headings as the collection of classification categories. FIGS. 35-40, further described below, comprise a group of Figures (PATTERN 1) that show the HOME PAGE screen displays. FIGS. 35[B-1] and 38[W-1] show the initial HOME PAGE screen display at system startup. To begin research, a practice name ("Immigration") [26] is checked. FIGS. 36[B-1] and 39[W-1] show the HOME PAGE screen display after activating the research menus [l]-[4] by clicking the PRACTICE-NAME MENU [9] "Immigration" box [26] and "OK" button [19] in FIG. 35[B-1]. FIGS. 37[B-1] and 40[W-1] continue from FIGS. 36[B-1] and 39[W-1], respectively, and show the entry of a search request [22] in the SEARCH MENU [4] . FIGS. 41-54, further described below, comprise a group of Figures (PATTERN 2) that show screen displays for table-of- contents entries (i.e., classification categories with table- of-contents positions). FIG. 41[B-2] shows the screen display after clicking the TABLE-OF-CONTENTS MENU [1] "Concept" button in FIG. 36[B-1] to display (in "Concept" order) all black-letter statement identifiers (narrow, summary, and adjunct), starting at the highest level black-letter statement identifiers, linked to the practice name of "Immigration" selected in FIG. 35[B-1]. FIG. 42[B-2] shows the screen display after clicking the "+" button [16] in FIG. 41[B-2] to expand the selected black- letter statement identifier ("§4") one level. FIG. 43[B-2] shows the screen display after clicking the "+" button [16] in FIG. 42[B-2] to expand the selected black- letter statement identifier ("4.8.2.9.3") one level. FIG. 44[B-2] shows the screen display after clicking the TABLE-OF-CONTENTS MENU [1] "Compliance" button in FIG. 36[B-1] to display (in "Compliance" order) all black-letter statement identifiers, starting at the highest level black-letter statement identifiers, linked to the practice name of "Immigration" selected in FIG. 35[B-1]. FIG. 45[B-2] shows the screen display after clicking the "+" button [16] in FIG. 44[B-2] to expand the selected black- letter statement identifier ("§4") one level. FIG. 46[B-2] shows the screen display after clicking the "+" button [16] in FIG. 45[B-2] to expand the selected black- letter statement identifier ("4.8.2.1.4") one level. FIG. 47[B-2] shows the screen display after clicking the TABLE-OF-CONTENTS MENU [1] "Reg §" button in FIG. 36[B-1] to display (in "Reg §" order) all primary-source item identifiers (i.e., for regulations), starting at the highest level (i.e., regulation title), linked to the practice name of "Immigration" selected in FIG. 35[B-1]. FIG. 48[B-2] shows the screen display after clicking the "+" button [16] in FIG. 47[B-2] to expand the selected regulation title ("20 CFR") one level. (Note that only regulation sections linked, via narrow black-letter statement identifiers, to the practice name of "Immigration," per the selection in FIG. 35[B-1], are displayed.) FIG. 49[B-2] shows the screen display after clicking the "OK" button [19] in FIG. 48[B-2] to display the selected regulation ("20 CFR § 655.734") with its linked black-letter statement identifiers. FIG. 50[W-2] shows the screen display after clicking the TABLE-OF-CONTENTS MENU [1] "Key Number" button in FIG. 39[W-1] to display (in "Key Number" order) all West® Key Number Headings, starting at the Topic level, linked to the practice name of "Immigration" selected in FIG. 35[B-1]. FIG. 51[W-2] shows the screen display after clicking the "+" button [16] in FIG. 50[W-2] to expand the selected West® Key Number Topic ("ALIENS") one level. FIG. 52[W-2] shows the screen display after clicking the "+" button [16] in FIG. 51[W-2] to expand the selected West® Key Number Sub-Topic ("III. IMMIGRATION") one level. FIG. 53[W-2] shows the screen display after clicking the "+" button [17] m FIG. 50[W-2] to expand the selected West® Key Number Topic ("HABEAS CORPUS") one level. FIG. 54[W-2] shows the screen display after clicking the "+" button [16] in FIG. 53[W-2] to expand the selected West® Key Number Sub-Topic ("I. IN GENERAL") one level. FIGS. 55-58, further described below, comprise a group of Figures (PATTERN 3) that show screen displays for index terms. FIG. 55[B-3] shows the screen display after clicking the INDEX MENU [2] "A" button in FIG. 36[B-1] to display an index wordwheel [23] (with user-input box [22]), starting from the selected letter "A, " with all topical-index terms linked to the practice name of "Immigration" selected m FIG. 35[B-1]. FIG. 56[B-3] continues from FIG. 55[B-3] and shows clicking the topical-index term [26] ("Actual wage") . FIG. 57[W-3] shows the screen display after clicking the INDEX MENU [2] "A" button in FIG. 39[W-1] to display an index wordwheel [23] (with user-input box [22]), starting from the selected letter "A, " with all Descriptive-Word Index terms linked to the practice name of "Immigration" selected n FIG. 38 [W-l] . FIG. 58[W-3] continues from FIG. 57[W-3] and shows clicking the Descriptive-Word Index term [26] ("Adjustment of status") . FIGS. 59-65, further described below, comprise a group of Figures (PATTERN 4) that show screen displays for lists of primary-source citations (i.e., primary-source item identifiers) . FIG. 59[B-4] shows the screen display after clicking the PRIMARY-SOURCE MENU [3] "Reg §" button in FIG. 36[B-1] to display a wordwheel [23] with Code of Federal Regulation titles for the regulations linked to the practice name of "Immigration" selected n FIG. 35[B-1]. FIG. 60[B-4] continues from FIG. 59[B-4] and shows clicking a regulation title [26] , thereby displaying, in a second wordwheel [25] , the initial regulation sections for the selected regulation title. FIG. 61[B-4] continues from FIG. 60[B-4] and shows entering alphanumeric characters ("655.73") m a user-input box [22] and then clicking a regulation section [26] ("655.730 (d) ") . FIG. 62[B-4] shows the screen display after clicking the PRIMARY-SOURCE MENU [3] "Admm Cite" button in FIG. 36[B-1] to display a wordwheel [23] with a list of administrative materials linked to the practice name of "Immigration" selected in FIG. 35[B-1]. FIG. 63[B-4] continues from FIG. 62[B-4] and shows clicking an administrative reporter [26] and then entering an administrative-decision citation m user-input boxes [24]. FIG. 64[W-4] shows the screen display after clicking the PRIMARY-SOURCE MENU [3] "Case Cite" button in FIG. 39 [W-l] to display a wordwheel [23] with a list of law reporters with cases linked to the practice name of "Immigration" selected m FIG. 38 [W-l] . FIG. 65[W-4] continues from FIG. 64[W-4] and shows clicking a case reporter [26] and then entering a case citation m user-input boxes [24] . FIGS. 66-72, further described below, comprise a group of Figures (PATTERN 5) that show screen displays for the text of primary sources. FIG. 66[B-5] shows the screen display after clicking the "SUBMIT" button [20] in FIG. 61[B-4] to display the full text of the selected regulation subsection ("20 CFR § 655.730(d)"). FIG. 67 [B-5] shows the screen display after clicking a hypertext link [30] in FIG. 131[B-15] to display the full text of the selected form instructions. FIG. 68 [B-5] shows the screen display after clicking the "SUBMIT" button [20] in FIG. 63[B-4] to display the full text of the selected administrative decision ("Matter of Michael Hertz Associates") . FIG. 69 [B-5] shows the screen display after clicking a hypertext link [30] in FIG. 68 [B-5] to display the full text of the selected administrative decision ("Matter of Huckenbeck") . FIG. 70 [B-5] shows the screen display after clicking the OPTIONS MENU [8] "Insert" button in FIG. 69 [B-5] to open a new window in which to enter an annotation in user-input box [22] and save it by clicking the "OK" button [19] . (NOTE: The annotation window can be superimposed over any Figure in GUI PATTERNS 1-16.) FIG. 71[W-5] shows the screen display after clicking the "SUBMIT" button [20] in FIG. 65[W-4] to display the full text of the selected Supreme Court decision ("Reno v. Catholic Social Services"). FIG. 72[W-5] shows the screen display after clicking the down arrow [21] of the vertical scroll bar in FIG. 71[W-5] to move down several pages of text. FIGS. 73-74, further described below, comprise a group of Figures (PATTERN 6) that show screen displays for citations (i.e., primary- or secondary-source item identifiers) of full- text search results. FIG. 73[B-6] shows the screen display after clicking the SEARCH MENU [4] "SUBMIT" button in FIG. 37[B-1]. FIG. 74 [W-6] shows the screen display after clicking the SEARCH MENU [4] "SUBMIT" button in FIG. 40 [W-l]. FIGS. 75-76, further described below, comprise a group of Figures (PATTERN 7) that show screen displays for the text of full-text search results. In each PATTERN 7 Figure, the text of the document containing the hit is displayed starting at the first paragraph that satisfies the full-text search criteria . FIG. 75[B-7] shows the screen display after clicking the citation [31] of a search hit in FIG. 73[B-6] . FIG. 76[W-7] shows the screen display after clicking the citation [31] of a search hit in FIG. 7 [W-6] . FIGS. 77-87, further described below, comprise a group of Figures (PATTERN 8) that show screen displays for table-of- contents entries selected in PATTERN 2 or PATTERN 12 Figures. In each PATTERN 8 Figure, the selected table-of-contents entry [28] is highlighted and repositioned at the top of its window, and the LINK MENU [7] is activated. FIG. 77[B-8] shows the screen display after clicking the V LINK" button 11] in FIG. 43[B-2] . FIG. 78 [I 8] shows the screen display after clicking the LINK" button 11] in FIG. 46[B-2] . FIG. 79[B 8] shows the screen display after clicking the LINK" button 11] in FIG. 49 [B-2] . FIG. 80[B 8] shows the screen display after clicking the LINK" button 11] in FIG. 102 [B-12] . FIG. 81[B-8] shows the screen display after clicking the 'LINK" button 11] in FIG. 80[B-8] or the "LINK" button [12; in FIG. 102[B-12] FIG. 82 [B' 8] shows the screen display after clicking the "LINK" button 11] in FIG. 112 [B-12] . FIG. 83[B- 8] shows the screen display after clicking the SEQUENCE MENU 5] "Reg §" button in FIG. 82[B-8]. FIG. 84 [W' 8] shows the screen display after clicking the "LINK" button 11] in FIG. 52 [W-2] . FIG. 85 [ - 8] shows the screen display after clicking the "LINK" button 11] in FIG. 54 [W-2] . FIG. 86[W-8] shows the screen display after clicking the 'LINK" button 11] in FIG. 108 [W-12] FIG. 87[W-8] shows the screen display after clicking the "LINK" button [11] in FIG. 117 [W-12]. FIGS. 88-91, further described below, comprise a group of Figures (PATTERN 9) that show screen displays for index terms selected m PATTERN 3 or PATTERN 13 Figures. In each PATTERN 9 Figure, the selected index term [28] is highlighted and repositioned at the top of its window, and the LINK MENU [7] is activated. FIG. 88 [B-9] shows the screen display after clicking the "LINK" button [11] in FIG. 56.B-3]. FIG. 89 [B-9] shows the screen display after clicking the "LINK" button [11] in FIG. 118 [B-13] . FIG. 90[W-9] shows the screen display after clicking the "LINK" button [11] in FIG. 58[W-3]. FIG. 91[W-9] shows the screen display after clicking the "LINK" button [11] in FIG. 119[W-13]. FIGS. 92-96, further described below, comprise a group of Figures (PATTERN 10) that show screen displays for primary- source items selected in PATTERN 5, PATTERN 7, or PATTERN 15 Figures. In each PATTERN 10 Figure, the selected primary- source item [28] (e.g., case paragraph, regulation subsection) is highlighted and repositioned at the top of its window, and the LINK MENU [7] is activated. FIG. 92[B-10] shows the screen display after clicking the "LINK" button [11] in FIG. 66 [B-5]. FIG. 93[B-10] shows the screen display after clicking the "LINK" button [11] in FIG. 68 [B-5] or FIG. 75[B-7]. FIG. 94[B-10] shows the screen display after clicking the "LINK" button [11] in FIG. 129[B-15]. FIG. 95[W-10] shows the screen display after clicking the "LINK" button [11] in FIG. 71[W-5]. FIG. 96[W-10] shows the screen display after clicking the "LINK" button [11] in FIG. 72 [W-5] or FIG. 128[W-15]. FIGS. 97-101, further described below, comprise a group of Figures (PATTERN 11) that show screen displays for secondary-source items selected in PATTERN 7 or PATTERN 16 Figures. In each PATTERN 11 Figure, the selected secondary- source item is highlighted and repositioned at the top of its window, and the LINK MENU [7] is activated. FIG. 97[B-11] shows the screen display after clicking the "LINK" button [11] in FIG. 132 [B-16] . FIG. 98[B-11] shows the screen display after clicking the "LINK" button [11] in FIG. 136 [B-16]. FIG. 99[W-11] shows the screen display after clicking the "LINK" button [11] in FIG. 142 [W-16] . FIG. 100[W-11] shows the screen display after clicking the "LINK" button [11] in FIG. 141 [W-16]. FIG. 101[W-11] shows the screen display after clicking the up arrow [21] of the vertical scroll bar m FIG. 100[W-11] to move up one screen. FIGS. 102-117, further described below, comprise a group of Figures (PATTERN 12) that show screen displays when the LINK MENU [7] "TC ENTRIES" button is clicked in any PATTERN 9- 11 or 13-16 Figures. In each PATTERN 12 Figure, a selected research item or finding-tool entry [28] (highlighted in the left window) is linked to table-of-contents entries [29] (highlighted m the right window) . FIG. 102 [B-12] shows the screen display after clicking the LINK MENU [7] "TC ENTRIES" button in FIG. 88 [B-9]. FIG. 103 [B-12] shows the screen display after clicking the "ALL" button [15] in FIG. 102 [B-12] to display all black- letter statement identifiers, starting at the highest level black-letter statement identifiers, linked to the practice name of "Immigration" selected in FIG. 35[B-1]. FIG. 104 [B-12] shows the screen display after clicking the "+" button [16] in FIG. 103 [B-12] to expand the selected black-letter statement identifier ("§4") one level. FIG. 105 [B-12] shows the screen display after clicking the down arrow [21] of the vertical scroll bar in FIG. 104 [B- 12] to move down one screen. FIG. 106 [B-12] shows the screen display after clicking the "+" button [16] in FIG. 104 [B-12] to expand the selected black-letter statement identifier ("4.8.2.9.3") one level. FIG. 107 [B-12] shows the screen display after clicking the SEQUENCE MENU [6] "Reg §" button in FIG. 102 [B-12]. FIG. 108 [W-12] shows the screen display after clicking the LINK MENU [7] "TC ENTRIES" button in FIG. 90[W-9]. FIG. 109 [W-12] shows the screen display after clicking the "ALL" button [15] in FIG. 108 [W-12] to display all West® Key Number Headings, starting at the Topic level, linked to the practice name of "Immigration" selected in FIG. 38 [W-l]. FIG. 110 [W-12] shows the screen display after clicking the "+" button [16] in FIG. 109 [W-12] to expand the selected West® Key Number Topic ("ALIENS") one level. FIG. Ill [W-12] shows the screen display after clicking the "+" button [16] in FIG. 110 [W-12] to expand the selected West® Key Number Sub-Topic ("III. IMMIGRATION") one level. FIG. 112 [B-12] shows the screen display after clicking the LINK MENU [7] "TC ENTRIES" button in FIG. 92[B-10]. FIG. 113 [B-12] shows the screen display after clicking the SEQUENCE MENU [6] "Reg §" button in FIG. 112 [B-12] or FIG. 114 [B-12] . FIG. 114 [B-12] shows the screen display after clicking the SEQUENCE MENU [6] "Form No." button in FIG. 112 [B-12] or FIG. 113[B-12] . FIG. 115 [B-12] shows the screen display after clicking the LINK MENU [7] "TC ENTRIES" button in FIG. 93[B-10]. FIG. 116 [W-12] shows the screen display after clicking the LINK MENU [7] "TC ENTRIES" button in FIG. 95[W-10]. FIG. 117 [W-12] shows the screen display after clicking the LINK MENU [7] "TC ENTRIES" button in FIG. 96[W-10]. FIGS. 118-119, further described below, comprise a group of Figures (PATTERN 13) that show screen displays when the LINK MENU [7] "INDEX TERMS" button is clicked in any PATTERN 8-12 or 14-16 Figures. In each PATTERN 13 Figure, a selected research item or finding-tool entry [28] (highlighted in the left window) is linked to index terms [29] (highlighted in the right window) . FIG. 118[B-13] shows the screen display after clicking the LINK MENU [7] "INDEX TERMS" button in FIG. 82[B-8]. FIG. 119[W-13] shows the screen display after clicking the LINK MENU [7] "INDEX TERMS" button in FIG. 96[W-10]. FIGS. 120-125, further described below, comprise a group of Figures (PATTERN 14) that show screen displays when the LINK MENU [7] "ALL PRIMARY SOURCES" or other primary-source item button is clicked in any PATTERN 8-13 or 15-16 Figures. In each PATTERN 14 Figure, a selected research item or finding-tool entry [28] (highlighted in the left window) is linked to primary-source citations [29] (highlighted in the right window) . FIG. 120[B-14] shows the screen display after clicking the LINK MENU [7] "ALL PRIMARY SOURCES" button in FIG. 82 [B- 8] . FIG. 121[B-14] shows the screen display after clicking the LINK MENU [7] "Code" button in FIG. 92[B-10]. FIG. 122[W-14] shows the screen display after clicking the LINK MENU [7] "Code" button in FIG. 96[W-10]. FIG. 123[W-14] shows the screen display after clicking the LINK MENU [7] "Cases" button in FIG. 86[W-8]. FIG. 124[W-14] shows the screen display after clicking the LINK MENU [7] "Cases" button in FIG. 96[W-10]. FIG. 125[B-14] shows the screen display after clicking the LINK MENU [7] "Forms" button in FIG. 92[B-10]. FIGS. 126-131, further described below, comprise a group of Figures (PATTERN 15) that show screen displays when a primary-source citation has been clicked in the right window of any PATTERN 14 Figure. In each PATTERN 15 Figure, a selected research item or finding-tool entry [28] (highlighted in the left window) is linked to the text of a primary-source item [29] (highlighted in the right window) . FIG. 126[B-15] shows the screen display after clicking the code citation [31] in FIG. 121[B-14]. FIG. 127[B-15] shows the screen display after clicking the up arrow [21] of the vertical scroll bar in FIG. 126[B-15] to move up one screen. FIG. 128[W-15] shows the screen display after clicking the case citation [31] in FIG. 123[W-14]. FIG. 129[B-15] shows the screen display after clicking the administrative-decision citation [33] in FIG. 120[B-14]. FIG. 130[B-15] shows the screen display after clicking the form citation [31] in FIG. 125[B-14]. FIG. 131[B-15] shows the screen display after clicking the up arrow [21] of the vertical scroll bar in FIG. 130[B-15] to move up one screen. FIGS. 132-142, further described below, comprise a group of Figures (PATTERN 16) that show screen displays when the LINK MENU [7] "ANALYSIS" button is clicked in any PATTERN 8-15 Figures. In each PATTERN 16 Figure, a selected research item or finding-tool entry [28] (highlighted in the left window) is linked to text of secondary-source items [29] (highlighted in the right window) . FIG. 132 [B-16] shows the screen display after clicking the LINK MENU [7] "ANALYSIS" button in FIG. 88 [B-9]. FIG. 133 [B-16] shows the screen display after clicking the down arrow [21] of the vertical scroll bar in FIG. 132 [B- 16] to move down one screen. FIG. 134 [B-16] shows the screen display after clicking the down arrow [21] of the vertical scroll bar in FIG. 133 [B- 16] to move down one screen. FIG. 135 [B-16] shows the screen display after clicking the down arrow [21] of the vertical scroll bar in FIG. 134 [B- 16] to move down one screen. FIG. 136 [B-16] shows the screen display after clicking the SEQUENCE MENU [6] "Reg §" button in FIG. 132 [B-16] . FIG. 137 [B-16] shows the screen display after clicking the down arrow [21] of the vertical scroll bar in FIG. 136 [B- 16] to move down one screen. FIG. 138 [W-16] shows the screen display after clicking the LINK MENU [7] "ANALYSIS" button in FIG. 86[W-8]. FIG. 139 [W-16] shows the screen display after clicking the down arrow [21] of the vertical scroll bar in FIG. 138 [W- 16] to move down one screen. FIG. 140 [W-16] shows the screen display after clicking the SEQUENCE MENU [6] "Code §" button in FIG. 138 [W-16] . FIG. 141 [W-16] shows the screen display after clicking the down arrow [21] of the vertical scroll bar in FIG. 140 [W- 16] to move down one screen. FIG. 142 [W-16] shows the screen display after clicking the LINK MENU [7] "ANALYSIS" button in FIG. 96[W-10]. IV. DETAILED DESCRIPTIONS OF PREFERRED EMBODIMENTS OF THE INVENTION A. Overview The present invention can be applied to any discipline that has multiple types of content that can be classified under a collection of classification categories of the discipline. See FIG. 1. Described herein m detail are two preferred embodiments of the present invention directed to law. The first embodiment uses a collection of classification categories (i.e., "narrow black-letter statement identifiers") that is designed and written specifically to enhance the utility of the system by taking advantage of all the available functionality. See FIG. 3[B]. The second preferred embodiment uses a collection of classification categories that is derived from current legal-research products. The embodiment discussed is based on one kind of collection of such classification categories, namely, West® Key Number Headings. See FIG. 4 [W] . Preferred embodiments of the present invention for law are made up of the following broad classes of components: legal content comprising a collection of classification categories, research materials, and finding tools; file structures comprising a first primary file structure, second primary file structure, and ancillary file structures; a file- building system; a file-processing system; and a file- processmg-system user interface. See FIG. 2. These components are described in detail below. B. Legal Content (1) Collection of classification categories Legal content comprises a collection of classification categories, research materials (that is, primary and secondary sources), and finding tools, as discussed below. Two embodiments are described below in detail. In one preferred embodiment, legal content is linked primarily via narrow black-letter statement identifiers. In an alternative preferred embodiment, legal content is linked primarily via West® Key Number Headings. (a) One preferred embodiment using a collection of narrow black-letter statement identifiers as the collection of classification categories In one preferred embodiment, a collection of narrow black-letter statement identifiers is used as the collection of classification categories through which all related research items and finding-tool entries are primarily linked. A narrow black-letter statement identifier is a short, descriptive heading for a narrow black-letter statement. A narrow black-letter statement comprises a narrow expression of black-letter law that represents one substantively distinct way that primary-source authorities define, qualify, or distinguish a single principle, proposition, or legally relevant fact of controlling law. Each narrow black-letter statement has one (and only one) narrow black-letter statement identifier. Each narrow black-letter statement identifier is unique (i.e., it cannot be used with more than one narrow black-letter statement). In this embodiment of the present invention computerized checks are run to insure compliance with this rule. The characteristics and methods of one preferred method for the creation of narrow black-letter statements (and the related summary black-letter statements with which the narrow black-letter statements are always displayed in the file- processing-system user interface) is described in detail in "Authoring black-letter legal content" below. (b) Alternative preferred embodiment using a collection of West® Key Number Headings as the collection of classification categories In an alternative preferred embodiment, a collection of West® Key Number Headings is used as the collection of classification categories through which all related research items and finding-tool entries are primarily linked. Computer processes convert all the existing associations (as reflected in West® publications) between the apposite parts of the West® Key Number System and related research items (i.e., case digests, cases, code and regulation sections cited in the case digests, and entries from West's® "Descriptive-Word Index") into a service developed under the present invention. In other embodiments, the tables of contents of existing publications can be similarly used as collections of classification categories - e.g., a concept-based patent-law treatise (e.g., "Chisum on Patents") of the sort published by Matthew Bender and Company or a code-based tax service (e.g., "Standard Federal Tax Reporter") of the sort published by CCH . The methods used to convert any such product into a service under the present invention will be substantially similar to the ones used for the West® Key Number System. Because the West® Key Number System is one of the most highly structured of the existing organizing schemes, it is examined in detail here as a model for the way the teachings of the present invention can be applied to build systems using collections of classification categories derived from current legal-research products . An embodiment of the present invention that employs a collection of classification categories designed and written specifically for the invention (e.g., "narrow black-letter statement identifiers") will deliver a higher level of functionality than an embodiment employing a collection of classification categories derived merely from current legal- research products (e.g., West® Key Number Headings or a treatise table of contents) . Thus, collections of classification categories derived from current legal-research products make it possible to take advantage of some, but not all the functionality offered by the present invention. For example, in such embodiments the linking may be limited to only some types of primary sources (e.g., cases and statutes), and resequencing of legal content may be limited to only one type of table-of-contents order (e.g., by concept). However, embodiments that use such classification categories still enable users to perform research much more efficiently than currently available legal-research products allow. Furthermore, editorial enhancements to the classification categories (i.e., to the breadth and precision of the categories and the number of links to related research items) prior to their conversion into a service under the present invention can substantially improve its functionality. (2) Research materials - primary sources Primary sources comprise original print or electronic materials created by public organizations, as described under "Primary sources" above. A research service in immigration law, such as the one used in the sample interface illustrated in FIGS. 35-142, would comprise the following primary sources: Title 8, United States Code and related code titles and sections; the immigration-related sections of Titles 8, 20, 22, 28, and 42 of the Code of Federal Regulations; Operations Instructions (Immigration and Naturalization Service), Foreign Affairs Manual (Dept. of State); Dictionary of Occupational Titles (Dept. of Labor); immigration-related cases in the U.S. Supreme Court, Courts of Appeals, and District Courts; precedent decisions of the INS and Board of Immigration Appeals; INS Administrative Appeals Unit Decisions; OCAHO decisions; BALCA Deskbook (Dept. of Labor); and Immigration Judges Handbook. Primary sources are made up of individual units of primary source (referred to herein as "primary-source items"), which comprise materials such as cases, code sections, regulations, and court rules. Each primary-source item has one (and only one) pπmary- source item identifier, which includes: a mandatory reference to the formal or customarily used citation (e.g., volume number, reporter name, and first page of a case; code section; rule number; form number) for the primary-source item. Such citations can be found in the "The Bluebook, A Uniform System of Citation" (Harvard Law Review Association) or "The Chicago Manual of Style" (University of Chicago Press). In addition, in the present invention, each primary-source item identifier includes an optional, supplementary reference to an internal citation to relevant text, as appropriate to the source (e.g., case paragraph number; code subsection; form box number) . Each primary-source item identifier is unique (i.e., it cannot be used with more than one primary-source item) . In this embodiment of the present invention computerized checks are run to insure compliance with this rule. (3) Research materials - secondary sources Secondary sources comprise print or electronic materials created primarily by private legal publishers to help the user find and analyze primary sources. (a) One preferred embodiment using a collection of narrow black-letter statement identifiers as the collection of classification categories In accordance with this preferred embodiment of the present invention, secondary sources are made up of individual units of secondary source (referred to herein as "secondary- source items") , each of which has an appropriate secondary- source item identifier, as follows: narrow black-letter statement identifiers, with mandatory corresponding text of narrow black-letter statements; summary black-letter statement identifiers, with optional corresponding text of summary black-letter statements; and author-comment identifiers, with mandatory corresponding text of author comments. (i) Narrow black-letter statements and statement identifiers As noted above, a narrow black-letter statement comprises a narrow expression of black-letter law that represents one substantively distinct way that primary-source authorities define, qualify, or distinguish a single principle, proposition, or legally relevant fact of controlling law. Each narrow black-letter statement has one (and only one) narrow black-letter statement identifier, which is a short, descriptive heading for the narrow black-letter statement. Each narrow black-letter statement identifier is unique (i.e., it cannot be used with more than one narrow black-letter statement) . In this embodiment of the present invention computerized checks are run to insure compliance with this rule. (ii) Summary black-letter statements and statement identifiers A summary black-letter statement comprises a self- standing unit that provides a brief, high-level summary of the legal principle ( s) , proposition (s) , or legally relevant facts expressed in one or more narrow black-letter statements. Each summary black-letter statement has one (and only one) summary black-letter statement identifier, which is a short, descriptive heading for the summary black-letter statement. Each summary black-letter statement identifier is unique (i.e., it cannot be used with more than one summary black- letter statement). In this embodiment of the present invention computerized checks are run to insure compliance with this rule . Both summary and narrow black-letter statements are essential to maximizing the functionality of this preferred embodiment of the present invention. Narrow black-letter statements (through their narrow black-letter statement identifiers) make it possible to offer great precision in linking to relevant research items and finding-tool entries. Summary black-letter statements (through their summary black- letter statement identifiers) facilitate the arrangement of research items and finding-tool entries (including narrow black-letter statements) into different sequences. The two types of statements complement one another. With narrow black-letter statements alone, the context for the principle or proposition it narrowly expresses might not be readily apparent to the user. With summary black-letter statements (which by their nature cover a broader range of principles) alone, linking to research items and finding-tool entries might lead to many marginally relevant items. Such potential problems are avoided through the use of both types of black-letter statements, which, given the present invention's architecture, makes it possible to display linked items together, as if the items comprised a single unit of information. Thus, in the file-processing-system and in the file-processing-system user interface of this embodiment, narrow black-letter statements always "travel" with the summary black-letter statements to which they are linked. This insures that even the most narrowly framed narrow black-letter statements, accompanied by their summary black-letter statements, are always self-standing - i.e., understandable to the user regardless of the context or sequence in which they may be viewed. (iii) Author comments and identifiers An author comment comprises an author's statement about the significance or practical consequences of legal principles, propositions, or legally relevant facts, and can take one of many forms - e.g., a discussion of controlling principles or unsettled law, practical guidance, an example of the application of legal rules to specific factual situations, a warning, an opinion, a suggestion, a news item, an annotation, a sample form or document. Each author comment has one (and only one) author-comment identifier, which is a short, descriptive heading for an author comment. Each author- comment identifier is unique (i.e., it cannot be used with more than one author comment) . In this embodiment of the present invention computerized checks are run to insure compliance with this rule. (b) Alternative preferred embodiment using a collection of West® Key Number Headings as the collection of classification categories In this preferred embodiment of the present invention, the secondary-source items are West® case digests, which are individual summaries of the points of law or fact contained in one or more paragraphs of a case. A case digest may contain citations to other primary-source items (code sections, regulations) that relate to the point (s) of law embodied in the case digest. Each case digest has one (and only one) case-digest identifier, which is similar to a primary-source item identifier for cases, and includes: (a) a reference to the formal or customarily used citation for a case (e.g., volume number, reporter name, and first page number) , and (b) an additional reference to the internal paragraph within the case to which the West® case digest has been assigned. Each case- digest identifier is unique (i.e., it cannot be used with more than one case digest) . In a service under the present invention, computerized checks are run to insure compliance with this rule. (4) Finding tools Finding tools comprise: a table of practice names, tables of contents, a topical index, and tables of primary-source item identifiers. Note that full-text searching, although not a type of content, is another finding tool of the present invention. (a) Table of practice names A table of practice names is an ordered arrangement of all the practice names that are used in a service under the present invention. A practice name is a short, descriptive heading for a major area of legal practice - e.g., "Immigration," "Patents," "Personal Injury," "Taxation." Practice names make it possible for the publisher to combine several different legal practice areas into a single embodiment of the present invention and for the user to distinguish among them when doing research. Thus, in one preferred embodiment of the present invention, the system can encompass the legal content for a specific practice name (e.g., "Patents"), integrate the legal content for multiple practice names (e.g., "Patents," "Trademarks," "Trade Secrets," "Copyright," and "Tax"), or integrate the legal content for legal practice names and the practice names for other disciplines (e.g., within the discipline of law, "Personal Injury" and "Medical Malpractice," and within the discipline of medicine, "Obstetrics" and "Pediatrics") . (b) Tables of contents A table of contents is a system or schedule for classifying legal principles, issues, and legally relevant facts in the law or in an area of legal practice. (i) One preferred embodiment using a collection of narrow black-letter statement identifiers as the collection of classification categories In this preferred embodiment, tables of contents are made up of three types of entries, adjunct, summary, and narrow black-letter statement identifiers. See, for example, FIG. 41[B-2] for adjunct black-letter statement identifiers, FIG. 42[B-2] for summary black-letter statement identifiers, and FIG. 43[B-2] for narrow black-letter statement identifiers. First, adjunct black-letter statement identifiers comprise descriptive headings for related summary and narrow black-letter statement identifiers within a specific type of table-of-contents hierarchy. Adjunct black-letter statement identifiers are assigned alphanumeric table-of-contents positions that are superior to those of summary black-letter statement identifiers, and thus enhance the readability of a table of contents and make its high-level organization clear. Second, summary black-letter statement identifiers, as described above, are assigned alphanumeric table-of-contents positions in each type of table-of-contents hierarchy to which they are relevant. In each such hierarchy, the summary black- letter statement identifiers are superior to the narrow black- letter statement identifiers with which they are associated. Third, narrow black-letter statement identifiers, also described above, are assigned alphanumeric table-of-contents positions in each type of table-of-contents hierarchy to which they are relevant. The present invention may incorporate many different types of tables of contents, depending on the nature of the practice area. The following tables of contents are used in this preferred embodiment. First, a conceptual table of contents is a table of contents built around an ordered set of logical relationships - e.g., from general principles to more specific ones (this kind of table of contents is such as is most commonly used for legal treatises) . A conceptual table of contents must include all the adjunct black-letter statement identifiers, summary black-letter statement identifiers, and narrow black-letter statement identifiers within the area of legal practice. See FIGS. 41[B-2], 42[B-2] and 43[B-2]. Second, a transactional table of contents is a table of contents ordered by transactions (e.g., filing of a petition, appeal of an adverse determination) and their constituent steps as they occur in the area of legal practice. A transactional table of contents includes an appropriate subset of adjunct black-letter statement identifiers, summary black- letter statement identifiers, and narrow black-letter statement identifiers within the area of legal practice. Third, a chronological table of contents is a table of contents ordered by the time sequence in which legal issues or transactions (i.e., handling a particular task or matter) arise in a lawyer's practice. A chronological table of contents includes an appropriate subset of adjunct black- letter statement identifiers, summary black-letter statement identifiers, and narrow black-letter statement identifiers within the area of legal practice. Fourth, a compliance table of contents is a type of conceptual table of contents that only includes a subset of adjunct black-letter statement identifiers, summary black- letter statement identifiers, and narrow black-letter statement identifiers dealing with issues having a relevant time element for action. See FIGS. 44[B-2], 45[B-2] and 46 [B- 2] . (ii) Alternative preferred embodiment using a collection of West® Key Number Headings as the collection of classification categories In this alternate preferred embodiment, West® Key Number Headings are used as the classification categories and also serve as entries m a table of contents based on their assignments by their publisher to positions in a taxonomy of American law. A West® Key Number Heading consists of two elements which make it unique: (1) the Topic name (e.g., "ALIENS") and (2) the Key Number (e.g., "52"), referred to throughout West® Digests as "ALIENS 52." Each Topic name comprises an identification of a general area of American law. Each Key Number identifies a specific point of American law within the general area identified by a Topic name. In Westlaw® the Topics are numbered consecutively m alphabetical order using whole numbers (with occasional number and letter designations - e.g., "316a"), starting with "1" for "ABANDONED AND LOST PROPERTY," and ending with "414" for "ZONING AND PLANNING." (A special Topic "450" exists for "MERIT SYSTEMS PROTECTION.") In this scheme, the number for "ALIENS" is "24," so that in Westlaw® the designation "24k52" would be the equivalent of "ALIENS 52." Topics and Key Numbers are frequently displayed (m print and electronic media) with two other components to provide additional context: (1) Hierarchical classification information or Sub-Topics that organize groups of Key Numbers. FIG. 51 [W-2] illustrates the four Sub-Topics under "ALIENS." Some Topics have two or more levels of Sub-Topics. (2) A "Key Line" comprising a short description of the specific point of American law identified by a given Key Number under a given Topic Name. FIG. 52 [W-2] illustrates Key Lines for different Key Numbers under the Topic of "ALIENS" and the Sub-Topic of "IMMIGRATION." The Key Line for "ALIENS 52" is "Detention, supervision and deportation." ( c ) Index (i) One preferred embodiment using a collection of narrow black-letter statement identifiers as the collection of classification categories This preferred embodiment uses a topical index, which comprises an alphabetically ordered list of words and phrases (referred to herein as "topical-index terms") denoting principles, concepts, or legally relevant facts. Such topical- index terms are written for narrow black-letter statements. (ii) Alternative preferred embodiment using a collection of West® Key Number Headings as the collection of classification categories West's® Descriptive-Word Index is an alphabetically ordered list of words and phrases (referred to herein as "Descriptive-Word Index terms") denoting the principles, concepts, or legally relevant facts in West's® case digests. (d) Tables of primary-source item identifiers A table of primary-source item identifiers is an ordered arrangement of the primary-source item identifiers for a particular type of primary source. Such order is based on a logical arrangement of the information (e.g., by code section, by case citation) , such that a researcher who already knows the desired code section or case citation can find the related text. The lists are constructed automatically by the system from the primary-source item identifiers. (In current legal- research products, such lists are often called "tables of authorities," or, more specifically, "tables of cases," "tables of statutes," "tables of regulations," and the like.) (5) Authoring methods for one preferred embodiment using a collection of narrow black-letter statement identifiers as the collection of classification categories (a) Narrow black-letter statement identifiers and narrow black-letter statements defined Since narrow black-letter statement identifiers, as implemented in this preferred embodiment, generally have no direct counterpart in currently available legal-research products, an overview of one process by which narrow black- letter statement identifiers are created for processing and display within a computerized system of the present invention is provided below. The narrow black-letter statement identifiers used as classification categories are derived from narrow black-letter statements . A narrow black-letter statement in law is defined as "a narrow expression of black-letter law that represents one substantively distinct way that primary-source authorities define, qualify, or distinguish a single principle, proposition, or legally relevant fact of controlling law." Each narrow black-letter statement has an identifier, which is a short, descriptive heading for the narrow black-letter statement. In accordance with the present invention, the specific terms used in the above definition have the following meaning: "controlling law" - the legal principle or proposition expressed by the narrow black-letter statement reflects the currently accepted rule of law. Thus, no narrow black-letter statements would express the principles for a repealed code section or an overruled judicial decision. However, narrow black-letter statements would cover law that was currently being interpreted in alternative ways - e.g., where there are conflicting views among the federal circuits. "define, qualify, or distinguish" - this is the level of detail expressed by a primary-source authority. A separate narrow black-letter statement exists for every such substantively distinct expression. "legal principle, proposition, or legally relevant fact" - the legal principle or proposition expressed by the narrow black-letter statement is derived from: (1) the plain text of a code section or regulation, (2) interpretation of the law by a court or administrative agency, (3) court rules of practice, (4) administrative and executive policies and orders, (5) international agreements, (6) facts that are important to how a court or administrative agency applies the law. "one substantively distinct way" - each narrow black-letter statement must be distinguishable from every other narrow black-letter statement based on substance, not an alternative way of expressing the same principle. A principle stated in a general way and the same principle stated in a qualified form are substantively different. "primary-source authorities" - narrow black-letter statements are based solely on the expressions of primary- source items . Any narrow black-letter statement and its identifier is made self-standing (i.e., understandable to the user regardless of the context or sequence in which displayed) by its display in the GUI with the summary black-letter statement and its identifier to which the narrow black-letter statement identifier is linked. A summary black-letter statement in law is defined as "a summary of the principle (s) , proposition (s) , or legally relevant fact(s) expressed in one or more narrow black-letter statements." A summary black-letter statement identifier is a short, descriptive heading for the summary black-letter statement from which it is derived. (b) Drafting rules for narrow black-letter statements Existing primary and secondary authorities typically express legal principles in a manner that requires the reader to refer, or have access, to related introductory or explanatory materials (e.g., other sections of a treatise; treatise table of contents; other paragraphs in a case; other subsections of a code) . Thus, it is assumed that the context for a particular statement of principle will be supplied by other materials. This is one reason why, as noted above, current legal-research products present information in one linear sequence and in one classification scheme - there is no ready way for publishers to identify the dependent and independent statements within their products, or to identify which statements must always be displayed in combined form to provide sufficient context for the reader. By contrast, each narrow black-letter statement is drafted according to strict rules and is presented in the GUI in a manner that insures that the expression of each principle is comprehensible to the user no matter how the narrow black- letter statement is displayed - i.e., whether alone or in different sequences with other narrow black-letter statements. This is accomplished in two fundamental ways: First, each narrow black-letter statement is linked to, and in the GUI "travels" with, a summary black-letter statement . Second, a separate narrow black-letter statement is written for each different way, from general to specific, that primary-source authorities define, qualify, or distinguish the principle or proposition. These rules are summarized in Tables 1-3, followed by text examples in Tables 4-10, below. Referring to Table 1 immediately below: There is only one primary-source item (e.g., a regulation subsection) that discusses three principles PI, P2, and P3. Thus, a narrow black-letter statement derived from that primary-source item can express PI, P2, and P3 in combination. However, if other primary-source items subsequently address PI or P2 or P3 separately, additional narrow black- letter statements must be written to reflect such primary- source coverage. Referring to Table 2 below: Some relevant primary source authorities express principles PI, P2, and P3 alone, some express them in different combinations. Thus, narrow black-letter statements derived from those primary- source items will express PI, P2, and P3 individually. Because it is so common in law to have several primary- source items address the same legal principle, the situation shown in Table 2 is far more likely to arise than that in Table 1. Thus, as a matter of efficient writing, the rules of Table 1 could be restated as shown in Table 3 immediately below, where three narrow black-letter statements are written instead of one. Tables 4-7 immediately below provide examples of the application of the rules set forth in Table 3 above. Tables 4- 6 show typical summary black-letter statements (SBLS) and their identifiers (SBLS-ID) and narrow black-letter statements (NBLS) and their identifiers (NBLS-ID) . Table 4: SBLS- -ID: "NOTICE ATTESTATION" SBLS: "In completing the Labor Condition Application for H-1B nonimmigrants, employers must attest that notice of the LCA filing has been provided all workers at the place of employment, either through the bargaining representative, or, in the absence thereof, through posting a copy of the LCA at the place of employment." NBLS- -ID: "NOTICE OF LCA TO BARGAINING REPRESENTATIVE" NBLS: "Notice must be given to the bargaining representative up to 30 days prior to the date the labor condition application (Form ETA-9035) is filed." Table 5 SBLS- -ID: "WAGE DEDUCTIONS FROM H-1B EMPLOYEES" SBLS: "During the period of H-1B employment, the employer must comply with strict rules as to making acceptable deductions from the required wage payments . " NBLS- -ID: "UNAUTHORIZED WAGE DEDUCTION EQUIVALENT TO NONPAYMENT" NBLS: "An unauthorized deduction from the required wage is the equivalent to nonpayment for purposes of Department of Labor investigation and enforcement." Table 6 SBLS- I D : "H- 1B VI SA TERM" SBLS: "The H-1B visa validity period for specialty occupations or fashion models is three years with a three-year renewal." NBLS-ID: "VISA PETITION VALID FOR THREE YEARS" NBLS: "An approved H-1B visa petition for specialty occupations or fashion models is valid for a period of up to three years." Referring to Table 6 above: if another primary-source authority were to further define, qualify, or distinguish the principle or proposition expressed therein, a new narrow black-letter statement would be required, as shown in Table 7 below. Table 7 SBLS- -ID: "H-1B VISA TERM" SBLS: "The H-1B visa validity period for specialty occupations or fashion models is three years with a three-year renewal." NBLS- -ID: "MEASURING H-1B VALIDITY PERIOD" NBLS "The validity period for H-1B visa petitions commences on the petition approval date or requested start date, whichever occurs later, and ends on the requested completion date, but in no event exceeds the minimum of three years or the validity period of the labor condition application." Tables 8-10 immediately below show how narrow black- letter statements are derived from primary-source items, specifically, a federal regulation. 20 CFR § 655.760(a) provides m part: "PUBLIC EXAMINATION. The employer shall make a filed labor condition application and necessary supporting documentation available for public examination at the employer's principal place of business in the U.S. or at the place of employment within one working day after the date on which the labor condition application is filed with DOL. The following documentation shall be necessary: (1) ... (2) ... (3) ... (4) ... (5) ..." Since some other primary-source authorities refer to the elements m the initial paragraph of 20 CFR § 655.760(a) generally and some specifically, some collectively and some individually, the paragraph must be rewritten as three narrow black-letter statements per the rules set out m Table 3 above . Table 8 SBLS- -ID: "PUBLIC FILE" SBLS: "Upon filing a Labor Condition Application (Form ETA-9035) for an H-1B nonimmigrant, the employer must make a public file of documentation available for inspection." NBLS- -ID: "EMPLOYER MUST CREATE PUBLIC FILE OF LCA AND DOCUMENTATION" NBLS: "The employer of an H-1B nonimmigrant must make the filed Labor Condition Application and supporting documentation available for public examination." Table 9 SBLS-ID: [Same as Table 8 above.] SBLS: [Same as Table 8 above.] NBLS-ID: "LCA PUBLIC FILE MUST BE MADE AVAILABLE WITHIN ONE DAY OF FILING" NBLS: "The Labor Condition Application public file must be made available for public examination within one working day after the date on which the Labor Condition Application is filed with DOL Table 10 SBLS- -ID: [Same as Table 8 above.] SBLS: [Same as Table 8 above.] NBLS- -ID: "LCA PUBLIC FILE MUST BE MADE AVAILABLE AT PLACE OF BUSINESS OR EMPLOYMENT" NBLS: "The Labor Condition Application public file must be made available for public examination at the employer's principal place of business in the U.S. or at the place of employment." In the file-processing-system user interface, when materials, such as those in Tables 8-10, are displayed together consecutively, the same summary black-letter statement and its identifier, which is linked to each narrow black-letter statement identifier, would only be displayed one time . (c) Authoring methods for narrow black-letter statement embodiment As discussed above, the present invention can use different types of collections of classification categories. In the case of collections of classification categories derived from current legal-research products, computer- readable versions (e.g., those used in the publisher's photocomposition process) of the classification categories and the implicit or explicit relationships between the classification categories and related research items and finding-tool entries, are automatically processed using the teachings of the present invention. A collection of classification categories (e.g., a collection of narrow black-letter statement identifiers) may also be designed and written specifically to enhance the utility of the system by taking advantage of all the available functionality. Before the file-building system can be used, publishers, authors and editors may employ writing and editorial methods that are similar to those used for prior-art products to create and organize secondary-source items (i.e., summary black-letter statements, narrow black-letter statements, author comments, and their respective identifiers) and specify links between narrow black-letter statement identifiers, on the one hand, and related research items and finding-tool entries, on the other hand. There are many existing authoring and editorial systems suitable to the task of creating narrow black-letter statement identifiers and linking them to other legal content. The optimum method in a given situation will depend on the form in which the primary-source materials with which the author (s) must work are stored, on a legal publisher's existing tools for creating legal publications, and on the vehicle the publisher intends to use for delivery of the information (e.g., the Internet, CD-ROM). One possible editorial method is described below in general terms to further clarify the nature of narrow black-letter statements, their relation to other research items and finding-tool entries, and the structure of the files used by the file-building system of the present invention. No attempt is made to specify all the functionality of a publisher's editorial system or the most efficient work methods. In the 16 STEPS set forth below, it is assumed that the author's writing and editing operations are performed with one of the commercially available HTML editors (such as SoftQuad's HoTMetaL PRO or Microsoft Publisher). The use of an HTML editor may facilitate distributed writing and editing operations using the Internet. However, the present invention is not so limited and any equivalent programs/methods known to those skilled in the art may be employed. Moreover these steps are illustrative of but one preferred embodiment of the present invention. STEP 1: DIVIDING THE WORK As shown in STEP 1 of the flowchart in FIG. 5 [B] , authors preparing content for use in the present invention, like authors of existing publishers preparing to create a conventional treatise, (a) divide a practice area (such as immigration law) into substantially self-standing subareas (i.e., into natural divisions of a practice area, of the sort reflected at the highest level of the table of contents of treatise - e.g., see left frame of FIG. 41[B-2]), and (b) where feasible, make an initial allocation of primary-source items to each of the subareas. This division of subject matter and primary-source items permits multiple authors and editors to work simultaneously, but is not an essential prerequisite to the creation of a service employing a collection of narrow black-letter statement identifiers. STEP 2: WRITING NARROW BLACK-LETTER STATEMENTS AND NARROW BLACK-LETTER STATEMENT IDENTIFIERS As shown in STEP 2 of the flowchart in FIG. 5 [B] , (a) Using a standard HTML editor, the author opens two files in split-screen mode (Windows A and B) : (i) In Window A, an HTML template (see FIG. 5 [B] ) that specifies (A) one "narrow black-letter statement" text field in which to write the narrow black-letter statement, (B) one "narrow black- letter statement identifier" link field in which to enter the corresponding narrow black-letter statement identifier, (C) multiple "primary-source item identifier" link fields in which to enter the primary-source item identifiers (of cases, code sections, regulations, and the like) to which the narrow black-letter statement identifier is relevant, and (D) multiple "practice name" link fields m which to enter practice name(s) to which the narrow black-letter statement identifier is relevant, and (11) In Window B, a file of the selected primary-source items . (Note that primary-source items [such as cases] have been preprocessed by computer and software to assign a field identification [for example, NAME, CITE, OPINION] and paragraph numbers within fields to each primary-source item. These field identifications and paragraph numbers, along with the identification of the primary-source item [for example, a case citation], will be targets to be inserted m link fields, as described in STEP 3(a) below.) The author prioritizes the sequence m which the primary-source items will be reviewed for purposes of writing narrow black- letter statements. With respect to immigration law, the first primary source to be analyzed is the Code of Federal Regulations. This prioritization of primary-source items expedites the work of the authors, but is not an essential prerequisite to the creation of a service employing narrow black-letter statements. (b) The author reads the primary-source items in Window B, identifies the principles and propositions, and, as appropriate m Window A, (l) writes one narrow black-letter statement in its designated text field and the corresponding narrow black-letter statement identifier in its designated link field. As each narrow black-letter statement / narrow black-letter statement identifier pair is completed, the author goes to STEP 3(a); and/or (n) using the summarizing capabilities of the authoring system, finds a previously written record containing a narrow black-letter statement / narrow black-letter statement identifier pair to which the primary-source item is relevant. As each previously written narrow black-letter statement identifier is found, the author goes to STEP 3 (a) . STEP 3: ASSIGNING PRACTICE NAMES AND PRIMARY-SOURCE ITEM IDENTIFIERS TO NARROW BLACK-LETTER STATEMENT IDENTIFIERS CREATED IN STEP 2 As shown m STEP 3 of the flowchart m FIG. 5 [B] , (a) In Window A, for the narrow black-letter statement identifier m its designated link field, the author enters (see FIG. 9[B] for record layout) : (l) one or more practice names (to which the narrow black-letter statement identifier is relevant) in their designated link fields, and (n) one or more primary-source item identifiers (to which the narrow black-letter statement identifier is relevant) in their designated link fields. (Note that when updating previously written narrow black-letter statement identifiers, per STEP 2(b) (n) above, the author will be adding to practice name(s) or primary-source item identifier (s) that have previously been entered in their designated link fields per STEPS 3(a) (I) and 3(a) (11) immediately above.) (b) When all practice names and primary-source item identifiers for a given narrow black-letter statement identifier are entered m their link fields, the author writes the record, and then goes back to STEP 2 (b) . (c) The author continues the cycle described in STEPS 2(b), 3(a) and 3(b) until (I) in Window B, all primary-source items for a practice subarea are reviewed, (n) in Window A, (A) all narrow black-letter statement / narrow black-letter statement identifier pairs derived from the primary-source items are written and entered in their respective text and link fields, and (B) the practice names and primary-source item identifiers (to which the narrow black-letter statement identifier is relevant) are entered m their respective link fields of the appropriate narrow black-letter statement record, and (m) all records are written. (d) The author closes the file m Window B. STEP 4: CONSTRUCTING A PROVISIONAL CONCEPTUAL TABLE OF CONTENTS FROM THE NARROW BLACK-LETTER STATEMENT IDENTIFIERS CREATED IN STEP 2 As shown m STEP 4 of the flowchart in FIG. 5 [B] , (a) Using the HTML editor, the author opens, in Window B, an HTML template for a conceptual table of contents that specifies multiple link fields m which to enter narrow black- letter statement identifiers. (b) The author copies and rearranges all the narrow black-letter statement identifiers from their link fields m Window A into the order of a conceptual table of contents m Window B. The HTML template enables the author to represent the logical relationships among the narrow black-letter statement identifiers by arranging them at different levels m the table-of-contents hierarchy - i.e., from general principles to more specific ones. (c) The author saves and closes the file in Window B. The author closes the file in Window A. (d) The author invokes software that constructs a provisional conceptual table of contents by assigning a provisional conceptual table-of-contents position to each narrow black-letter statement identifier from the file created m Window B STEP 4(b) . The output file is made up of records, each comprising two link fields: (l) a provisional conceptual table-of-contents position and (n) the narrow black-letter statement identifier to which the table-of-contents position is relevant. (Note: This file is created to assist the author in completing STEP 5; it will be used by the flle-buildmg system after having been updated in STEPS 7(b) and 10(b).) STEP 5: WRITING SUMMARY BLACK-LETTER STATEMENTS AND SUMMARY BLACK-LETTER STATEMENT IDENTIFIERS As shown in STEP 5 of the flowchart in FIG. 5 [B] , (a) Using the HTML editor, the author opens two files in split-screen mode (Windows A and B) : (1) In Window A, an HTML template that specifies (A) one "summary black-letter statement" text field m which to write the summary black- letter statement, (B) one "summary black-letter statement identifier" link field in which to enter the corresponding summary black-letter statement identifier, and (C) multiple "narrow black-letter statement identifier" link fields m which to enter narrow black-letter statement identifiers to which the summary black-letter statement identifier is relevant, (n) In Window B, a file of the provisional conceptual table of contents (i.e., narrow black-letter statement identifiers with positions m the conceptual table of contents) created in Window B STEP 4(d). (b) The author reads the table-of-contents entries in Window B, and, as appropriate, in Window A, writes one summary black-letter statement in its designated text field and the corresponding summary black-letter statement identifier m its designated link field. As each summary black-letter statement / summary black-letter statement identifier pair is completed, the author goes to STEP 6(a). STEP 6: ASSIGNING SUMMARY BLACK-LETTER STATEMENT IDENTIFIERS TO NARROW BLACK-LETTER STATEMENT IDENTIFIERS As shown in STEP 6 of the flowchart in FIG. 5 [B] , (a) For the summary black-letter statement identifier m its designated link field m Window A, the author copies one or more narrow black-letter statement identifiers (to which the summary black-letter statement identifier is relevant) from the "narrow black-letter statement identifier" link fields in Window B into the "narrow black-letter statement identifier" link fields m Window A. (Note: more than one narrow black-letter statement identifier may be assigned to each summary black-letter statement identifier, but a single narrow black-letter statement identifier may not be assigned to more than one summary black-letter statement identifier.) (b) When all narrow black-letter statement identifiers for a given summary black-letter statement identifier are entered in their link fields, the author writes the record, and then goes back to STEP 5(b). (c) The author continues the cycle described in STEPS 5(b), 6(a) and 6(b) until (1) in Window B, all table-of- contents entries are reviewed, (11) m Window A, (A) all summary black-letter statement / summary black-letter statement identifier pairs are written and entered m their respective text and link fields, and (B) the narrow black- letter statement identifiers (from Window B) to which the summary black-letter statement identifier is relevant are copied into the "narrow black-letter statement identifier" link fields of the appropriate summary black-letter statement record, and (m) all records are written. (d) The author closes the files m Windows A and B. STEP 7 : MERGING SUMMARY NARROW BLACK-LETTER STATEMENT IDENTIFIERS FROM STEP 6 INTO THE PROVISIONAL CONCEPTUAL TABLE- OF-CONTENTS CREATED IN STEP 4 As shown in STEP 7 of the flowchart in FIG. 6[B], The author invokes software that automatically creates a provisional conceptual table of contents, as follows: (a) Summary black-letter statement identifiers (from the file created m Window A STEP 6(c)) are added to the existing provisional conceptual table of contents made up of narrow black-letter statement identifiers with table-of-contents positions (from the file created m STEP 4(d)) . The computer assigns a provisional conceptual table-of- contents position to each entry (i.e., to each summary and each narrow black-letter statement identifier) m the resulting expanded conceptual table of contents created in STEP 7 (a) . The output file is made up of records, each comprising three link fields: (i) a provisional conceptual table-of-contents position and, as relevant, either (ii) a summary black-letter statement identifier or (iii) a narrow black-letter statement identifier. (Note: This file is created to assist the author in completing STEP 8; it will be also used by the file-building system after having been updated in STEP 10 (b) . ) STEP 8: WRITING ADJUNCT BLACK-LETTER STATEMENT IDENTIFIERS As shown m STEP 8 of the flowchart in FIG. 6[B], (a) Using the HTML editor, the author opens two files m split-screen mode (Windows A and B) : (l) In Window A, an HTML template that specifies (A) one "adjunct black-letter statement identifier" link field m which to enter an adjunct black-letter statement identifier, and (B) one "table-of- contents position" link field in which to enter the table-of- contents position of the first summary black-letter statement identifier that would follow the adjunct black-letter statement identifier m a conceptual table of contents, (n) In Window B, a file of the provisional conceptual table of contents (i.e., narrow and summary black-letter statement identifiers with positions in the conceptual table of contents) created m STEP 7(b) . (b) The author reads the conceptual table-of-contents entries m Window B, and, as appropriate, in Window A, writes one adjunct black-letter statement identifier in its designated link field. As each adjunct black-letter statement identifier is completed, the author goes to STEP 9(a). STEP 9: ASSIGNING CONCEPTUAL TABLE-OF-CONTENTS POSITIONS TO ADJUNCT BLACK-LETTER STATEMENT IDENTIFIERS As shown in STEP 9 of the flowchart in FIG. 6[B], (a) For the adjunct black-letter statement identifier in its designated link field in Window A, the author copies a table-of-contents position for a relevant summary black-letter statement identifier from the "table-of-contents position" link fields in Window B. (b) After each table-of-contents position for a given adjunct black-letter statement identifier is entered in its link field, the author writes the record, and then goes back to STEP 8 (b) . (c) The author continues the cycle described in STEPS 8(b), 9(a) and 9(b) until (i) in Window B, all conceptual table-of-contents entries (Window B) are reviewed, (ii) in Window A, all adjunct black-letter statement identifier / table-of-contents position pairs are entered in their respective link fields, and (iii) all records are written. (d) The author closes the files in Windows A and B. STEP 10: MERGING ADJUNCT BLACK-LETTER STATEMENT IDENTIFIERS FROM STEP 9 INTO THE PROVISIONAL CONCEPTUAL TABLE OF CONTENTS CREATED IN STEP 7(B) TO CREATE A COMPLETE CONCEPTUAL TABLE OF CONTENTS As shown in STEP 10 of the flowchart in FIG. 7 [B] , The author invokes software that automatically creates a complete conceptual table of contents, as follows: (a) Adjunct black-letter statement identifiers with table-of-contents positions (from the file created in STEP 9(c) - Window A) are added to the existing provisional conceptual table of contents made up of narrow and summary black-letter statement identifiers with table-of-contents positions (from the file created in STEP 7(b)) . (b) The computer assigns a conceptual table-of-contents position - to each adjunct, summary and narrow black-letter statement identifier in the resulting complete conceptual table of contents. The output file is made up of records, each comprising two link fields of (i) a conceptual table-of- contents position and, as relevant, (ii) an adjunct black- letter statement identifier, a summary black-letter statement identifier, or a narrow black-letter statement identifier. (Note: This file replaces the file created in STEP 7(b) .) STEP 11: CONSTRUCTING OTHER TABLES OF CONTENTS As shown in STEP 11 of the flowchart in FIG. 7 [B] , (a) Using the HTML editor, the author opens two files m split-screen mode (Windows A and B) : (l) in Window A, the file created in STEP 10(b), and (ii) in Window B, an HTML template for narrow black-letter statement identifiers. (b) The author copies and rearranges the narrow black- letter statement identifiers relevant to a particular type of table of contents from their link fields in Window A into the order of such table of contents m Window B (e.g., a transactional or chronological or compliance table of contents). The HTML template enables the author to represent the logical relationships among the narrow black-letter statement identifiers by arranging them at different levels in the particular table-of-contents hierarchy. (c) The author saves and closes the file m Window B. The author closes the file m Window A. (d) The author invokes software that automatically creates a provisional table of contents for the particular type of hierarchy, as follows: (I) Summary black-letter statement identifiers (from the file created m Window A STEP 6(c)) are added to the narrow black-letter statement identifiers copied into table-of-contents positions in STEP 11(b) . (ii) The computer assigns a provisional table-of- contents position appropriate to the particular type of table of contents - to each entry (i.e., to each summary and narrow black-letter statement identifier) in the resulting file created in STEP 11(d) (l) . The output file is made up of records, each comprising two link fields of (I) a provisional table-of-contents position, and, as relevant, (ii) a summary black-letter statement identifier or a narrow black-letter statement identifier. (Note: This file is created to assist the author in completing STEP 11 (e) ; it will be used by the flle-building system after having been updated m STEP 11 (h) . ) (e) Using the HTML editor, the author opens two files in split-screen mode (Windows A and B) : (1) In Window A, an HTML template that specifies (A) one "adjunct black-letter statement identifier" link field m which to enter an adjunct black-letter statement identifier, and (B) one "table-of- contents position" link field m which to enter the table-of- contents position of the first summary black-letter statement identifier that would follow the adjunct black-letter statement identifier in the particular type of table of contents, (ii) In Window B, a file of the provisional table of contents (i.e., narrow and summary black-letter statement identifiers with positions m the table of contents) created in STEP 11 (d) (n) . (f) The author reads the table-of-contents entries in Window B, and, as appropriate, in Window A, writes one adjunct black-letter statement identifier m its designated link field. After each adjunct black-letter statement is completed, the author copies a table-of-contents position for a relevant summary black-letter statement identifier from the "table-of- contents position" link fields m Window B. The author then writes the record and repeats this STEP 11(f) . (g) When all adjunct black-letter statement identifier / table-of-contents position pairs are completed as described m STEP 11(f), the author closes the files m Windows A and B. (h) The author invokes software that automatically creates a complete table of contents m the particular hierarchy (e.g., transactional, chronological, compliance), as follows: (I) Adjunct black-letter statement identifiers with table-of-contents positions (from the file created in Window A STEP 11(f)) are added to the existing provisional table of contents made up of narrow and summary black-letter statement identifiers with table-of-contents positions (from the file created m STEP 11(d) (ii)). (n) The computer assigns a table- of-contents position appropriate to the particular type of table of contents - to each adjunct, summary and narrow black- letter statement identifier in the resulting complete table of contents. The output file is made up of records, each comprising four link fields: (i) a table-of-contents position and, as relevant, either (ii) an adjunct black-letter statement identifier, (iii) a summary black-letter statement identifier, or (iv) a narrow black-letter statement identifier. (Note: This file replaces the file created in STEP 11(d) (ii) .) (i) The author repeats the process described in STEPS 11(a) - 11(h) for other tables of contents (e.g., transactional, chronological, compliance). STEP 12: MERGING ADJUNCT BLACK-LETTER STATEMENT IDENTIFIERS, SUMMARY NARROW BLACK-LETTER STATEMENTS AND THEIR IDENTIFIERS, AND NARROW BLACK-LETTER STATEMENTS AND THEIR IDENTIFIERS INTO A SINGLE FILE. As shown in STEP 12 of the flowchart in FIG. 8 [B] , as an aid in writing author comments and topical-index terms, the author invokes software that merges the complete conceptual table-of-contents ile created in STEP 10 (b) (made up of adjunct, summary, and narrow black-letter statement identifiers with table-of-contents positions) with the corresponding text of summary and narrow black-letter statements created in STEPS 5(b) and 2(b), respectively. (Note: This file resembles the layout of a typical legal treatise in which chapter and section headings (the "identifiers") are followed by their associated text (the "statements") ; such file is created to assist the author in completing STEPS 13-16, but is not used by the file-building system. ) Note that for types of tables of contents that are primary-source-centric (e.g., arranged by primary-source item identifier such as citing case or code section or regulation section or form number or rule number) , the file-building system will automatically generate the appropriate table-of- contents sequence for such primary-source item identifiers and for the narrow black-letter statement identifiers linked to them. STEP 13: WRITING AUTHOR COMMENTS AND AUTHOR-COMMENT IDENTIFIERS As shown in STEP 13 of the flowchart in FIG. 8 [B] , (a) Using the HTML editor, the author opens two files in split-screen mode (Windows A and B) : (i) In Window A, an HTML template (see FIG. 10 [B] ) that specifies (A) one "author comment" text field in which to write the author comment, (B) one "author-comment identifier" link field in which to enter the author-comment identifier for the author comment, and (C) multiple "narrow black-letter statement identifier" link fields in which to enter narrow black-letter statement identifiers to which the author comment and its identifier are relevant, (ii) In Window B, the file created in step 12 (i.e., of adjunct black-letter statement identifiers, summary narrow black-letter statements and their identifiers, and narrow black-letter statements and their identifiers). (b) The author reads the text in Window B, and, as appropriate, in Window A, writes one author comment in its designated text field and the corresponding author-comment identifier in its designated link field. As each author comment / author-comment identifier pair is completed, the author goes to STEP 14(a). STEP 14: ASSIGNING AUTHOR-COMMENT IDENTIFIERS TO NARROW BLACK- LETTER STATEMENT IDENTIFIERS As shown in STEP 14 of the flowchart in FIG. 8 [B] , (a) For the author-comment identifier in its designated link field in Window A, the author copies one or more narrow black-letter statement identifiers (to which the author- comment identifier is relevant) from their link fields in Window B into the "narrow black-letter statement identifier" link fields in Window A. (b) When all narrow black-letter statement identifiers for a given author-comment identifier are entered m their link fields, the author writes the record, and then goes back to STEP 13 (b) . (c) The author continues the cycle described in STEPS 13(b), 14(a) and 14(b) until ( ) m Window B, all narrow black-letter statements and their identifiers are reviewed, (ii) m Window A, (A) all author-comment / author-comment identifier pairs are written and entered in their respective text and link fields, and (B) the narrow black-letter statement identifiers (from Window B) to which the author- comment identifier is relevant are copied into the "narrow black-letter statement identifier" link fields of the appropriate author-comment record, and (in) all records are written . (d) The author closes the file m Window A. STEP 15: WRITING TOPICAL-INDEX TERMS FOR NARROW BLACK-LETTER STATEMENTS As shown m STEP 15 of the flowchart in FIG. 8 [B] , (a) Using the HTML editor, the author opens, in Window A, an HTML template that specifies (I) one "topical-mdex term" link field in which to write the topical-mdex term, and (n) multiple "narrow black-letter statement identifier" link fields in which to enter narrow black-letter statement identifiers to which the topical- dex term is relevant. (b) The author reads the text in Window B (which is still open from Step 14 above) , and, as appropriate, in Window A, writes one topical-mdex term in its designated link field. As each topical-mdex term is completed, the author goes to STEP 16(a) . STEP 16: ASSIGNING TOPICAL-INDEX TERMS TO NARROW BLACK-LETTER STATEMENT IDENTIFIERS As shown in STEP 16 of the flowchart in FIG. 8 [B] , (a) For the topical-index term in its designated link field in Window A, the author copies one or more narrow black- letter statement identifiers (to which the topical-index term is relevant) from their link fields in Window B into the "topical-index term" link fields in Window A. (b) When all narrow black-letter statement identifiers for a given topical-index term are entered in their link fields, the author writes the record, and then goes back to STEP 15 (b) . (c) The author continues the cycle described in STEPS 15(b), 16(a) and 16(b) until (i) in Window B, all narrow black-letter statements and their identifiers are reviewed, (ii) in Window A, (A) all topical-index terms are written and entered in their link fields, and (B) the narrow black-letter statement identifiers (from Window B) to which the topical- index term is relevant are copied into the "narrow black- letter statement identifier" link fields of the appropriate topical-index term record, and (iii) all records are written. (d) The author closes the files in Windows A and B. C. File structures This preferred embodiment of the present invention uses files and supporting indices comprising two primary file structures and one or more ancillary file structures. The file structures described herein can be implemented at a single site or distributed over multiple sites that intercommunicate via a wide-area network such as the Internet. The first primary file structure comprises a set of display and full-text search files, comprising a serial file, an inverted index, and an index of hypertext links, together with supporting indexes, to enable retrievable storage of research items, full-text searching of research items, and hypertext linking. The second primary file structure comprises a set of files having relational capability, built from computer- readable legal content. The relational capability is implemented through two-member sets of a classification category and a research item or finding-tool entry. Some ancillary file structures enable the building of menus of practice names, table-of-contents sequences for the collection of classification categories, categories of topical-mdex terms, types of primary source, and full-text- search options. Other ancillary file structures support various housekeeping functions. Despite the identity in form between relational tables and certain forms of indexes, in the discussion that follows the phrase "relational table" is restricted to the files that directly implement the logic of the second primary file structure. "Index" is used for other pointer files in both the first and second primary file structures. The foregoing file structures are now described m detail . (1) First primary file structure The first primary file structure is that which supports interactive full-text search and retrieval. Interactive full- text search and retrieval is a technology well known to practitioners of the art. It permits the user to search by words and phrases appearing in text of legal content, and then to display retrieved materials in a variety of sequences and formats. Full-text technology has a wide variety of implementation methods (e.g., Boolean searching and "natural- language" searching, the latter most frequently implemented with statistical techniques) . Likewise, full-text technology has been implemented with a variety of supporting file structures and searching mechanisms, including (i) a linear scan of the serial (linear) file in which the text is stored in the sequence in which it occurs in the research materials (for small files), and (ii) a variety of searchable indexes containing the searchable words from the linear file; most popular are inverted indexes, signature files, and hash tables. Examples of full-text systems include products from Fulcrum Technologies (e.g., Ful- Text) and Folio (e.g., Views) . The implementation of full-text searching and display in the interactive text-search-and-retrieval system included in the present invention is somewhat similar to that in the Lexis® and Westlaw® research systems. It uses a serial (or linear) file, an inverted index, an index to the serial file, and an index of hypertext links for each separately searchable type of legal content (federal-court cases, administrative decisions, federal codes, federal regulations, narrow black- letter statements, author comments, and the like). A serial (or linear) file comprises text that is divided into fields and stored in the sequence in which it occurs in the primary and secondary sources. A common form of part of a document in the serial file is shown in FIG. 11. Using case law as an example, Table 11 immediately below illustrates the division of a primary-source item (that is, of a record in the full-text serial file) into fields or segments. The type of cases selected are decisions of the U.S. Supreme, Circuit, and District Courts relating to immigration matters, as well as administrative decisions under the Immigration and Nationalization Act. A given case may not have all segments. Other primary-source items are similarly segmented. Table 11 CITE: The citation (volume and page number location) of the case in a reporter (e.g., 432 F. Supp. 1234) . DATE: The date the case was decided. COURT The name of the court in which the case was heard. NAME: The complete name of all the parties involved in the case. SHORT-NAME A generally accepted abbreviation of the contents of the NAME field. HISTORY: The prior history of the matter, before it reached the current court. NUMBER: The docket number (s) assigned to the case by the court . HEADNOTES : Legal issues that are pertinent to the case, as provided by the court or by an external editorial process . OPINION: The majority opinion or the only opinion. DISSENT: The dissenting opinion(s), if any. CONCUR: The concurring opinion (s), if any. OPINIONBY: The name(s) of the judge (s) writing the majority opinion or the only opinion. CONCURBY: The name(s) of the judge (s) writing the concurring opinion (s), if any. DISSENTBY: The name(s) of the judge (s) writing the dissenting opinion (s), if any. COUNSEL: The name of any person representing a party in the case. An inverted index comprises searchable words that are stored m lexicographic sequence, each searchable word containing a pointer to all its occurrences in the serial file. (To save space in the inverted index, approximately 100 very common words of little or no value m searches ["stop words"], such as "and" and "but," accounting for approximately fifty percent of the text of legal materials, are not stored the inverted index.) . A common form of inverted-index entries is shown in FIG. 12. An index to the serial file points from primary and secondary-source item identifiers to the locations of the corresponding text in the serial file. See FIG. 13. Hypertext technology is widely used with materials in interactive text-search-and-retrieval systems to incorporate links ("hypertext links") between a citation (cross-reference) put in the text of one document by its author (e.g., a case in which the judge cites an earlier case m support of a particular proposition) , and the apposite text of the cited document stored elsewhere in the computer and software of the system. Such hypertext links are conventionally implemented by tagging the citation (cross-reference) as it appears m the citing document so that it can be flagged to the user as an available hypertext link (e.g., by making the text a different color) , and storing with the tag, m a form not visible to the user, the address of the location m the cited document. When the user clicks on the visible form of the citation (cross- reference) m the citing document, the computer and software of the system use the invisible form of the address to retrieve and display the text of the cited document. Links between the citing document and cited document (with tags in a form not visible to the user) are stored in indexes. See FIG. 14. (2) Second primary file structure The second primary file structure supports links between classification categories and other kinds of legal content in the system. It is most conveniently implemented as a relational database. As is well known, a relational database system (made up of relational tables) is a type of database management system that stores information in tables - rows and columns of data. The rows of a table represent records (collections of information about items) and the columns represent fields (particular attributes of a record) . A relational database system retrieves and combines materials by using data in specified columns of one table to find data in another table - i.e., by matching information in a field or fields of one table with information in a corresponding field or fields of other tables. Examples of commercially available software for relational databases include products from Oracle (e.g., Oracle VIII) and Microsoft (e.g., Access). (a) One preferred embodiment using a collection of narrow black-letter statement identifiers as the collection of classification categories In this preferred embodiment, narrow black-letter statement identifiers are linked via relational tables to a variety of other kinds of legal content (e.g., cases, code sections, regulations, court rules, summary black-letter statements, narrow black-letter statements, topical index terms, table-of-contents positions, and practice names). In addition, summary and adjunct black-letter statement identifiers are linked via relational tables to table-of- contents positions. Such links are assigned both programmatically and by authors and editors as part of the writing and editorial process. The links are manipulated by the present invention's file-processing system in a manner invisible to the researching user. To implement such linkages in the present invention, relational tables store links (two-way pointers): First, between a narrow black-letter statement identifier and a primary-source item identifier, which points in turn (through the indexing method of the interactive text-search- and-retrieval system) to the location in a serial file of the text of the primary-source item; between a narrow black-letter statement identifier and a summary black-letter statement identifier (only one) (if the summary black-letter statement identifier has a corresponding summary black-letter statement, the summary black-letter statement identifier points, through the indexing method of the interactive text-search-and- retrieval system, to the location in a serial file of the text of its summary black-letter statement) ; and between a narrow black-letter statement identifier and an author-comment identifier, which points in turn (through the indexing method of the interactive text-search-and-retrieval system) to the location in a serial file of the text of the author comment. Second, between a narrow black-letter statement identifier and a finding-tool entry such as a practice name, a topical-index term, and a conceptual table-of-contents position (and, in addition, as relevant, a chronological table-of-contents position, a transactional table-of-contents position, and a compliance table-of-contents position) . Third, between a summary black-letter statement identifier and a finding-tool entry such as a conceptual table-of-contents position (and, in addition, as relevant, a chronological table-of-contents position, a transactional table-of-contents position, and a compliance table-of-contents position) . Fourth, between an adjunct black-letter statement identifier and a finding-tool entry such as a conceptual table-of-contents position (and, in addition, as relevant, a chronological table-of-contents position, a transactional table-of-contents position, and a compliance table-of-contents position) . See FIG. 15 for a conceptual overview of the links and FIG. 16 [B] for the links as implemented between narrow black- letter statement identifiers and other legal content. Tables of primary-source item identifiers order primary sources in sequences customary for research in current legal- research products; for example, cases are ordered by their citations (i.e., by reporter name, volume number, and initial- page number) , and codified statutes are ordered by section and subsection number. These lists serve as finding tools for the researcher who already knows the citation of a desired case, or the section number of a desired statute. Links between primary-source item identifiers and their positions in tables of primary-source item identifiers are stored in indexes, similar to the relational tables used for narrow black-letter statement identifiers and table-of- contents positions described above. The link between a narrow black-letter statement identifier and other kinds of legal content in this embodiment of the present invention enables, according to well-known principles of relational technology, both direct and indirect links : First, bi-directional direct linking: given a link between them, from a narrow black-letter statement identifier to a specific research item or finding-tool entry, and from a specific research item or finding-tool entry to a narrow black-letter statement identifier. See FIG. 18. Second, a first indirect linking derived from the bidirectional direct linking: given the common link of a narrow black-letter statement identifier, then, from one research item or finding-tool entry (e.g., a regulation) to another research item or finding-tool entry (e.g., a case, a topical- index term) - i.e., (within the system, invisibly to the user) from a regulation to a narrow black-letter statement identifier linked to that regulation, and from that narrow black-letter statement identifier to all cases and topical- index terms linked to that narrow black-letter statement identifier. See FIG. 19. Third, a second indirect linking derived from the bidirectional direct linking: given the common link of a research item or finding-tool entry (e.g., a regulation), then from one narrow black-letter statement identifier to another narrow black-letter statement identifier. See FIG. 19. Fourth, chaining of links: given the direct and indirect linking described in the preceding three paragraphs, then the chaining of all such linked research items and finding-tool entries in any and all permutations and combinations. See FIG. 20. (b) Alternative preferred embodiment using a collection of West® Key Number Headings as the collection of classification categories In this alternative preferred embodiment, West® Key Number Headings are linked via relational tables to a variety of other kinds of legal content (e.g., cases, code sections, regulations, court rules, case digests, Descriptive-Word Index terms, table-of-contents positions, and practice names) . Such links are assigned programmatically using implicit linkages already present in the West® computer-readable representations of the above materials. The links are manipulated by the present invention's file-processing system in a manner invisible to the researching user. To implement such linkages in the present invention, relational tables store links (two-way pointers): First, between a West® Key Number Heading and a primary- source item identifier, which points in turn (through the indexing method of the interactive text-search-and-retrieval system) to the location in a serial file of the text of the primary-source item; and between a West® Key Number Heading and a case-digest identifier, which points in turn (through the indexing method of the interactive text-search-and- retrieval system) to the location in a serial file of the text of the case digest. Second, between a West® Key Number Heading and a finding- tool entry such as a practice name, a Descriptive-Word Index term and a conceptual table-of-contents position. See FIG. 15 for a conceptual overview of the links and FIG. 17 [W] for the links as implemented between West® Key Number Headings and other legal content. Tables of primary-source item identifiers order primary sources in sequences customary for research in current legal- research products; for example, cases are ordered by their citations (i.e., by reporter name, volume number, and initial- page number) , and codified statutes are ordered by section and subsection number. These lists serve as finding tools for the researcher who already knows the citation of a desired case, or the section number of a desired statute. Links between primary-source item identifiers and their positions in tables of primary-source item identifiers are stored in indexes, similar to the relational tables used for West® Key Number Headings and table-of-contents positions described above. The link between a West® Key Number Heading and other kinds of legal content in this embodiment of the present invention enables, according to well-known principles of relational technology, both direct and indirect links: First, bi-directional direct linking: given a link between them, from a West® Key Number Heading to a specific research item or finding-tool entry, and from a specific research item or finding-tool entry to a West® Key Number Heading. See FIG. 18. Second, a first indirect linking derived from the bidirectional direct linking: given the common link of a West® Key Number Heading, then, from one research item or finding- tool entry (e.g., a regulation) to another research item or finding-tool entry (e.g., a case, a Descriptive-Word Index term) - i.e., (within the system, invisibly to the user) from a regulation to a West® Key Number Heading linked to that regulation, and from that West® Key Number Heading to all cases and Descriptive-Word Index terms linked to that West® Key Number Heading. See FIG. 19. Third, a second indirect linking derived from the bidirectional direct linking: given the common link of a research item or finding-tool entry (e.g., a regulation), then from one West® Key Number Heading to another West® Key Number Heading. See FIG. 19. Fourth, chaining of links: given the direct and indirect linking described in the preceding three paragraphs, then the chaining of all such linked research items and finding-tool entries in any and all permutations and combinations. See FIG. 20. (3) Ancillary file structures (a) One preferred embodiment using a collection of narrow black-letter statement identifiers as the collection of classification categories In this preferred embodiment, ancillary file structures enable, among other things, the building of menus of practice names; table-of-contents sequences for adjunct, summary, and narrow black-letter statement identifiers; categories of topical-index terms; types of primary source; and full-text search options. Other ancillary file structures support various housekeeping functions. In general, such file structures are two-member indexes, with supporting indexes, to permit rapid access in different sequences. Such file structures are well known to practitioners of the art of interactive text information systems. (b) Alternative preferred embodiment using a collection of West® Key Number Headings as the collection of classification categories In this alternative preferred embodiment, ancillary file structures enable, among other things, the building of menus of practice names; table-of-contents sequences for West® Key Number Headings; categories of Descriptive-Word Index terms; types of primary source; and full-text search options. Other ancillary file structures support various housekeeping functions. In general, such file structures are two-member indexes, with supporting indexes, to permit rapid access in different sequences. Such file structures are well known to practitioners of the art of interactive text information systems . (4) Inter-relationships among file structures (a) One preferred embodiment using a collection of narrow black-letter statement identifiers as the collection of classification categories FIG. 21 [B] illustrates the inter-relationships among file structures in this preferred embodiment. FIG. 21 [B] represents all types of secondary sources and finding tools in this embodiment. However, immigration cases decided in the U.S. Supreme Court are used as a proxy for all the different types of possible primary sources. In FIG. 21 [B] , typographic conventions are: an outline of heavy, solid lines denotes a relational table; an outline of heavy, dashed lines denotes an inverted index file; an outline of light, solid lines denotes a serial (linear) file of text; an outline of light, dashed lines denotes one of the following indices - an index to the location of text in a serial file, an index of hypertext links, or an index of primary-source item identifiers in tables of primary-source item identifiers; and m the outlines that indicate relational tables and indexes, the sets of fields that contain linked information are separated by two colons, thus "::". In the first primary file structure, by function, the files are: First, full-text searching: m FIG. 21 [B] , the files that support full-text searching (the inverted index, the serial file, and the index to the serial file by primary or secondary source-item identifier) are shown in Boxes [35], [36], and [37] (for the text of immigration cases decided m the Supreme Court of the United States), in Boxes [42], [43], and [44] (for the text of narrow black-letter statements), in Boxes [46], [47], and [48] (for the text of summary black-letter statements), and in Boxes [50], [51], and [52] (for author comments) . Second, hypertext links: in FIG. 21 [B], Boxes [39], [40], and [36] illustrate the file structures for hypertext links between citing cross-references and the text referred to. Box [39] represents serial files of other primary-source items (cases, code sections) with cross-references imbedded m their text. The location (address) of a citing cross-reference is m an entry m the index shown in Box [40]; the same entry of the index also contains the location (address) of the text referred to in the serial file m Box [36] . In the second primary file structure, by function, the files are: First, relational tables for research items: in FIG. 21 [B] , Box [38] represents the relational table that links narrow black-letter statement identifiers to primary-source item identifiers for U.S. Supreme Court cases that are authority for those narrow black-letter statements. Box [49] represents the relational table that links narrow black-letter statement identifiers to summary black-letter statement identifiers. Box [53] represents the relational table that links narrow black-letter statement identifiers to author- comment identifiers. Second, relational tables and indexes for finding-tool entries: in FIG. 21 [B], Box [45] represents the relational table that links narrow black-letter statement identifiers to practice names. Box [54] represents the relational table that links narrow black-letter statement identifiers to topical- index terms. Boxes [55] and [56] represent the relational tables that link narrow black-letter statement identifiers to positions in conceptual and "other" (e.g., chronological) tables of contents. Boxes [57] and [58] represent the relational tables that link summary black-letter statement identifiers to positions in conceptual and "other" (e.g., chronological) tables of contents. Boxes [59] and [60] represent the relational tables that link adjunct black-letter statement identifiers to positions in conceptual and "other" (e.g., chronological) tables of contents. Box [41] represents the index that links primary-source item identifiers (case citations) to positions in a table of cases (for immigration cases decided in the U.S. Supreme Court) . (b) Alternative preferred embodiment using a collection of West® Key Number Headings as the collection of classification categories FIG. 22 [W] illustrates the inter-relationships among file structures in this preferred embodiment. FIG. 22 [W] represents all types of secondary sources and finding tools in this embodiment. However, immigration cases decided in the U.S. Supreme Court are used as a proxy for all the different types of possible primary sources. In FIG. 22 [W] , typographic conventions are: an outline of heavy, solid lines denotes a relational table; an outline of heavy, dashed lines denotes an inverted index file; an outline of light, solid lines denotes a serial (linear) file of text; an outline of light, dashed lines denotes one of the following indices - an index to the location of text in a serial file, an index of hypertext links, or an index of primary-source item identifiers in tables of primary-source item identifiers; and in the outlines that indicate relational tables and indexes, the sets of fields that contain linked information are separated by two colons, thus "::" In the first primary file structure, by function, the files are: First, full-text searching: in FIG. 22 [W] , the files that support full-text searching (the inverted index, the serial file, and the index to the serial file by primary or secondary source-item identifier) are shown in Boxes [35], [36], and [37] (for the text of immigration cases decided in the Supreme Court of the United States), and in Boxes [50], [51], and [52] (for the text of case digests) . Second, hypertext links: in FIG. 22 [W] , Boxes [39], [40], and [36] illustrate the file structures for hypertext links between citing cross-references and the text referred to. Box [39] represents serial files of other primary-source items (cases, code sections) with cross-references imbedded in their text. The location (address) of a citing cross-reference is in an entry in the index shown in Box [40]; the same entry of the index also contains the location (address) of the text referred to in the serial file in Box [36] . In the second primary file structure, by function, the files are: First, relational tables for research items: in FIG. 22 [W] , Box [38] represents the relational table that links West® Key Number Headings to primary-source item identifiers for U.S. Supreme Court cases that are authority for those West® Key Number Headings. Box [53] represents the relational table that links West® Key Number Headings to case-digest identifiers . Second, relational tables and indexes for finding-tool entries: in FIG. 22 [W] , Box [45] represents the relational table that links West® Key Number Headings to practice names. Box [54] represents the relational table that links West® Key Number Headings to Descriptive-Word Index terms. Box [55] represents the relational tables that link West® Key Number Headings to positions in a conceptual table of contents (i.e., the West® taxonomy of American law) . Box [41] represents the index that links primary-source item identifiers (case citations) to positions in a table of cases (for immigration cases decided in the U.S. Supreme Court) . D. File-building system The file-building system builds files and supporting indices comprising the first, second, and ancillary file structures described above. The files may be built entirely on one site, or on a distributed basis spread over multiple sites and connected by a communications network such as the Internet . (1) One preferred embodiment using a collection of narrow black-letter statement identifiers as the collection of classification categories At the conclusion of the black-letter authoring operations described above, the resulting HTML files are processed in order to create the files in the first and second primary file structures. (a) First primary file structure PRIMARY SOURCES For the primary sources used in the first primary file structure, the HTML files comprise cases, code sections, regulations and other primary-source items. See FIG. 23 [B] at [61]. These files were used in the authoring and editing process, but were not modified by those operations. The file-building system is employed, for each type of primary source, to extract and segment text (see FIG. 23 [B] at Step 1), and then to create the following files and indexes in the first primary file structure: (i) the serial file (see FIG. 23 [B] at Step 2); (ii) the index to the serial file from primary-source item identifiers (see FIG. 23 [B] at Step 3); (iii) the inverted index (see FIG. 23[B] at Step 4); and (iv) the index of hypertext links comprising a record for: (A) each primary-source item identifier for the citing document and the location of the cross-reference in its serial file, and (B) the primary-source or secondary-source item identifier, as the case may be, of the cited document and the location of the cross-reference in its serial file (see FIG. 23 [B] at Step 5). SECONDARY SOURCES AND FINDING TOOLS For secondary sources and finding tools used in the first primary file structure, the HTML files comprise: (i) A file, created in the authoring and editing operations, with records comprising (see FIG. 2 [B] at [62]): (A) 1 narrow black-letter statement, (B) 1 related narrow black-letter statement identifier, (C) 1-n primary-source item identifiers authors have linked to each narrow black-letter statement identifier, and (D) 1-n practice name(s) authors have linked to each narrow black-letter statement identifier, (ii) A file, created in the authoring and editing operations, with records comprising (see FIG. 24 [B] at [63]): (A) 1 summary black- letter statement, (B) 1 related summary black-letter statement identifier, and (C) 1-n narrow black-letter statement identifier (s) authors have linked to each summary black-letter statement identifier, (iii) A file, created in the authoring and editing operations, with records comprising (see FIG. 24 [B] at [64]): (A) 1 author comment, (B) 1 related author- comment identifier, and (C) 1-n narrow black-letter statement identifier (s ) authors have linked to each author-comment identifier . The file-building system is employed, for each type of secondary source (i.e., narrow black-letter statements, summary black-letter statements, and author comments), to extract and segment text (see FIG. 24 [B] at Step 6) by writing output records comprising the body and corresponding identifier of each type of secondary source, and then to create the following files and indexes in the first primary file structure: (i) the serial file (see FIG. 24 [B] at Step 7); (ii) the index to the serial file from the narrow black- letter statement identifiers, summary black-letter statement identifiers, and author-comment identifiers (see FIG. 24 [B] at Step 8); (iii) the inverted index (see FIG. 24 [B] at Step 9); and (iv) the index of hypertext links comprising a record for: (A) each secondary-source item identifier for the citing document and the location of the cross-reference in its serial file, and (B) the primary-source or secondary-source item identifier, as the case may be, of the cited document and the location of the cross-reference in its serial file (see FIG. 24 [B] at Step 10) . (b) Second primary file structure PRIMARY SOURCES The text of primary sources is not used in the second primary file structure. SECONDARY SOURCES AND FINDING TOOLS For secondary sources and finding tools used in the second primary file structure, the HTML files comprise: (i) The same three files used for secondary sources and finding tools in the first primary file structure described above - i.e., files with records containing text fields of narrow- black-letter statements, summary black-letter statements, and author comments (see FIG. 25 [B] at [62]-[64]). (ii) A file, created in the authoring and editing operations, with records comprising (see FIG. 25 [B] at [65]): (A) 1 topical-index term, and (B) 1-n narrow black-letter statement identifier ( s) authors have linked to each topical-index term, (iii) A file, created in the authoring and editing operations, with records comprising (see FIG. 25 [B] at [66]-[67]): (A) 1 table-of- contents position, -and- (B) 1 relevant adjunct black-letter statement identifier, -or- 1 relevant summary black-letter statement identifier, -or- 1 relevant narrow black-letter statement identifier (such table of contents may comprise a conceptual table of contents, a chronological table of contents, a compliance table of contents, and a transactional table of contents) . The file-building system is employed to create relational tables by extracting the link fields from the files described herein. See FIG. 25 [B] at Steps 11-16. A relational-table entry is created using (A) the primary link field (narrow black-letter statement identifier or summary black-letter statement identifier or adjunct black-letter statement identifier or author-comment identifier) together with (B) each of the other link field (s) . The creation of relational- table entries continues until all link fields in the record have been processed, resulting in the creation of the relational tables as shown in FIG. 25 [B], as follows: (i) from FIG. 25 [B] at [62] (narrow black-letter statement identifiers and primary-source item identifiers) to Step 11; (ii) from FIG. 25 [B] at [62] (narrow black-letter statement identifiers and practice names) to Step 12; (iii) from FIG. 25 [B] at [63] (narrow black-letter statement identifiers and summary black- letter statement identifiers) to Step 13; (iv) from FIG. 25 [B] at [64] (narrow black-letter statement identifiers and author- comment identifiers) to Step 14; (v) from FIG. 25 [B] at [65] (narrow black-letter statement identifiers and topical-index terms) to Step 15; and (vi) from FIG. 25 [B] at [66] -[67] (table-of-contents positions in different types of tables of contents and (A) adjunct black-letter statement identifiers, (B) summary black-letter statement identifiers, and (C) narrow black-letter statement identifiers) to Step 16. In addition, the file-building system is employed to create a sortable form of primary-source item identifier (from the text extracted and segmented in FIG. 23 [B] at Steps 1 and 3) . For each type of primary source (e.g., case, code section) an index is created using (A) the primary-source item identifier together with (B) its position in the apposite table of primary-source item identifiers (see FIG. 25 [B] at Step 17). (2) Alternative preferred embodiment using a collection of West® Key Number Headings as the collection of classification categories Computer-readable versions (e.g., those used in West's® photocomposition processes and Westlaw' s® file-building operations) of the classification categories and the implicit or explicit relationships between the West® Key Number Headings and related cases and case digests are automatically processed using the teachings of the present invention. (a) First primary file structure PRIMARY SOURCES For the primary sources used in the first primary file structure, the West® source files comprise cases, code sections, regulations and other primary-source items. See FIG. 26[W] at [61] . The file-building system is employed, for each type of primary source, to extract and segment text (see FIG. 26 [W] at Step 1), and then to create the following files and indexes in the first primary file structure: (i) the serial file (see FIG. 26 [W] at Step 2); (ii) the index to the serial file from primary-source item identifiers (see FIG. 26 [W] at Step 3); (iii) the inverted index (see FIG. 26[W] at Step 4); and (iv) the index of hypertext links comprising a record for: (A) each primary-source item identifier for the citing document and the location of the cross-reference in its serial file, and (B) the primary-source or secondary-source item identifier, as the case may be, of the cited document and the location of the cross-reference in its serial file (see FIG. 26 [W] at Step 5). SECONDARY SOURCES AND FINDING TOOLS For secondary sources and finding tools used in the first primary file structure, the files comprise files of West® Case Reporters with headnotes (see FIG. 27 [W] at [68]) from the West® editorial and composition system. First, the file-building system is employed to create records for case digests (see FIG. 27 [W] at Step 5A) , where each such record contains: (i) 1 "case digest" text field; (ii) 1 "case-digest identifier" link field; (iii) 1-n "primary-source item identifier" link fields; and (iv) 1-n "West® Key Number Heading" link fields. Second, the file- building system is employed to extract and segment the case- digest text (see FIG. 27 [W] at Step 6) by writing output records comprising the case digest and its corresponding identifier, and then to create the following files and indexes in the first primary file structure: (i) the serial file of case digests (see FIG. 27 [W] at Step 7); (ii) the index to the serial file from the case-digest identifiers (see FIG. 27 [W] at Step 8); (iii) the inverted index (see FIG. 27 [W] at Step 9); and (iv) the index of hypertext links comprising a record for: (A) each case-digest identifier for the citing document and the location of the cross-reference in its serial file, and (B) the primary-source or secondary-source item identifier, as the case may be, of the cited document and the location of the cross-reference in its serial file (see FIG. 27 [W] at Step 10) . (b) Second primary file structure PRIMARY SOURCES The text of primary sources is not used in the second primary file structure. SECONDARY SOURCES AND FINDING TOOLS For secondary sources and finding tools used in the second primary file structure, the West® source files comprise: (i) The same file used for secondary sources and finding tools m the first primary file structure described above - i.e., the file with records containing text fields of case digests (see FIG. 27 [W] at Step 5A; (11) a file of West's® Descriptive-Word Index and West® Key Number Headings (see FIG. 28 [W] at [69]); (in) a file of the taxonomy of West® Key Number System (published n front of each Topic m West® Case Digests) (see FIG. 28 [W] at [70]); and (iv) a file of West® Key Number Headings and practice names (see FIG. 28 [W] at [71] ) . The flle-buildmg system is employed to create relational tables by extracting the link fields from the files described herein. See FIG. 28 [W] at Steps 11-16. A relational-table entry is created using (A) the primary link field (West® Key Number Heading, Descriptive-Word Index term, or case-digest identifier) together with (B) each of the other link fιeld(s). The creation of relational-table entries continues until all link fields in the record have been processed, resulting in the creation of the relational tables as shown m FIG. 28 [W] , as follows: (l) from FIG. 27 [W] at Step 5A (West® Key Number Headings and primary-source item identifiers) to FIG. 28 [W] at Step 11; (n) from FIG. 27 [W] at Step 5A (West® Key Number Headings and case-digest identifiers) to FIG. 28 [W] at Step 12; (m) from FIG. 28 [W] at [69] (West® Key Number Headings and Descriptive-Word Index terms) to Steps 12A and 13; (iv) from FIG. 28 [W] at [70] (West® Key Number Headings and table- of-contents positions) to Steps 13A and 14; and (v) from FIG. 28 [W] at [71] (West® Key Number Headings and practice names) to Steps 13A and 15. In addition, the flle-buildmg system is employed to create a sortable form of primary-source item identifier (from the text extracted and segmented in Steps 1 and 3) . For each type of primary source (e.g., case, code section) an index is created using (A) the primary-source item identifier together with (B) its position m the apposite table of primary-source item identifiers (see FIG. 28 [W] at Step 16) . E. File-processing system The principal file-processing operations performed in response to commands from the user are set forth in this section. The commands are relayed from the user interface (e.g., a Web browser) over a communications network (e.g., the Internet) to the file-processing system. Operations common to large numbers of interactive systems - e.g., menu display, formatting and display of text - are not described. (1) For first primary file structure: interactive full-text search and retrieval The use of the file structures for interactive full-text search and retrieval can be illustrated in simplified fashion with an elementary Boolean search example - e.g., find all cases containing "wage" and "living" in a particular collection of cases. This is interpreted by the file- processing system to be a command to find all cases that contain, in whatever field, at least one occurrence of the word "wage" and at least one occurrence of the word "living:" First, the file-processing system retrieves from the inverted index the string of occurrences (document, field, paragraph, keyword position within paragraph) for the word "wage" and the string of occurrences (document, field, paragraph, keyword position within paragraph) for the word "living . " Second, the file-processing system compares the inverted- index entries of each string to one another. When it encounters the same document number in both strings, it records those entries as hits or matches. Third, from the list of hits or matches, the file- processing system can display to the user the names and cites of the cases that satisfy the full-text search request, their full text, passages of text around the occurrences of the words "wage" and "living" (KWIC, or Key Word in Context), and other formats. (2) For second primary file structure: relational tables for links between classification categories and other kinds of legal content (a) One preferred embodiment using a collection of narrow black-letter statement identifiers as the collection of classification categories This preferred embodiment uses a common narrow black- letter statement identifier to link all related research items or finding-tool entries to one another, and a common research item or finding-tool entry to link narrow black letter statements to one another. Specifically, the links between narrow black-letter statement identifiers, on the one hand, and research items and finding-tool entries, on the other hand, make it possible, via relational technology, for the computer and file-processing software of the system, (i) from a primary- or secondary-source item (e.g., a case, an author comment), to find one or more narrow black-letter statement identifier (s ) linked to that case or author comment, or, from a topical-index term, to find one or more narrow black-letter statement identifier (s) linked to that topical-index term, and (ii) from the same narrow black-letter statement identifier ( s) in (i) above to find all other research items and finding-tool entries (e.g., regulations, cases, author comments, topical- index terms) linked to the narrow black-letter statement identifier (s) (and which are therefore relevant to the same point of law as the case, author comment, or topical-index term in (i) above), and to enable the user to display any such identified research items or finding-tool entries as if such materials were linked directly to each other. In addition, the links between narrow black-letter statement identifiers and their positions in a conceptual (or a chronological or a transactional) table of contents, on the one hand, and between narrow black-letter statement identifiers and other research items and finding-tool entries in the computer and software of the system, on the other hand, make it possible, via relational technology, for the file- processing system (i) to assemble narrow black-letter statement identifiers into a conceptual table of contents, or a chronological table of contents, or a transactional table of contents, and (ii) to display selected research items linked to the narrow black-letter statement identifiers in one of the table-of-contents sequences in (ii) immediately above, resulting in the equivalent of a standard treatise, or practice guide, which the user can read as such. In summary, because all related legal content is linked via a common narrow black-letter statement identifier, the present invention permits a form of research that is not possible with any other legal-research tool known to the inventors: (i) given a research item or finding-tool entry, the file-processing system can find the narrow black-letter statement identifiers under which such research item or finding-tool entry has been editorially classified, and (ii) given a narrow black-letter statement identifier, the file- processing system can find all the research items and finding- tool entries that have been editorially classified to that narrow black-letter statement identifier. The user can continue, causing the file-processing system to repeat steps (i) and (ii) immediately above, iteratively, to explore relevant legal content to whatever extent desired. In so doing, the user can cause the file-processing system to select only certain kinds of legal content (e.g., cases) and to suppress the display of intervening narrow black-letter statement identifiers, if desired, so that only the selected legal content (e.g., cases) are displayed. The links between primary-source item identifiers and narrow black-letter statement identifiers, described above, further make possible the assembly of (i) linked narrow black- letter statement identifiers under one or more primary-source items sequenced in such a table of primary-source item identifiers, and (ii) other kinds of legal content linked to said narrow black-letter statement identifiers under one or more primary-source items sequenced in such a table of primary-source item identifiers. (b) Alternative preferred embodiment using a collection of West® Key Number Headings as the collection of classification categories This alternative preferred embodiment uses a common West® Key Number Heading to link all related research items or finding-tool entries to one another, and a common research item or finding-tool entry to link West® Key Number Headings to one another. Specifically, the links between West® Key Number Headings, on the one hand, and research items and finding-tool entries, on the other hand, make it possible, via relational technology, for the computer and file-processing software of the system, (i) from a primary- or secondary- source item (e.g., a case, a case digest), to find one or more West® Key Number Heading (s) linked to that case or case digest, or, from a Descriptive-Word Index term, to find one or more West® Key Number Heading (s) linked to that Descriptive- Word Index term, and (ii) from the same West® Key Number Heading (s) in (i) above to find all other research items and finding-tool entries (e.g., regulations, cases, case digests, Descriptive-Word Index terms) linked to the West® Key Number Heading (s) (and which are therefore relevant to the same point of law as the case, case digest, or Descriptive-Word Index term in (i) above), and to enable the user to display any such identified research items or finding-tool entries as if such materials were linked directly to each other. In addition, the links between West® Key Number Headings and their positions in a conceptual table of contents, on the one hand, and between West® Key Number Headings and other research items and finding-tool entries in the computer and software of the system, on the other hand, make it possible, via relational technology, for the file-processing system (i) to assemble West® Key Number Headings into a conceptual table of contents, and (ii) to display selected research items linked to the West® Key Number Headings in such table-of- contents sequence in (ii) immediately above, resulting in the equivalent of a standard treatise, which the user can read as such. In summary, because all related legal content is linked via a common West® Key Number Heading, the present invention permits a form of research that is not possible with any other legal-research tool known to the inventors: (i) given a research item or finding-tool entry, the file-processing system can find the West® Key Number Headings under which such research item or finding-tool entry has been editorially classified, and (ii) given a West® Key Number Heading, the file-processing system can find all the research items and finding-tool entries that have been editorially classified to that West® Key Number Heading. The user can continue, causing the file-processing system to repeat steps (i) and (ii) immediately above, iteratively, to explore relevant legal content to whatever extent desired. In so doing, the user can cause the file-processing system to select only certain kinds of legal content (e.g., cases) and to suppress the display of intervening West® Key Number Headings, if desired, so that only the selected legal content (e.g., cases) are displayed. The links between primary-source item identifiers and West® Key Number Headings, described above, further make possible the assembly of (i) linked West® Key Number Headings under one or more primary-source items sequenced in such a table of primary-source item identifiers, and (ii) other kinds of legal content linked to said West® Key Number Headings under one or more primary-source items sequenced in such a table of primary-source item identifiers. (3) For ancillary file structures The file-processing methods for ancillary file structures is a function of the file structure and its use (for example, display a menu of practice names) and are well known to practitioners of the art. (4) Overview of file processing in a typical research process (a) One preferred embodiment using a collection of narrow black-letter statement identifiers as the collection of classification categories The example below illustrates the relationships among the files involved in a typical research process, and provides an example of how the file-processing system accomplishes an indirect lookup using the common link of a narrow black-letter statement identifier. In this example, the user has found a regulation section which bears on the research problem directly and whose primary-source item identifier is "8 CFR § 655.3(b) ." He/she wants to find all the cases that discuss the issues arising in that regulatory section. The file-processing system finds the cases linked to the regulation by finding the narrow black- letter statement identifiers that are common to both: First, the file-processing system goes to the relational table that links narrow black-letter statement identifiers to one kind of primary-source item identifier (regulation sections) and finds all narrow black-letter statement identifiers linked to "§ 655.3(b)," as shown in Table 12 immediately below. Second, the file-processing system goes to the relational table that links narrow black-letter statement identifiers to another kind of primary-source item identifier (case citations) and finds the primary-source item identifiers of all cases linked to the narrow black-letter statement identifiers found in the first step, as shown in Table 13 immediately below. Third, the file-processing system goes to the index to the serial file that links case citations to the locations of the corresponding text of the cases in the serial file, and finds the location of all cases identified in the second step, as shown in Table 14 immediately below. Fourth, the file-processing system goes to the locations in the serial file of cases (identified in the third step) to retrieve the three relevant passages of cases - i.e., (1) Document: "119," Field: "Opinion," Paragraph: "5;" (2) Document: "213," Field: "Opinion," Paragraph: "123;" and (3) Document: "349," Field: "Opinion," Paragraph: "66." Fifth, the computer displays the text of the cases to the user , (b) Alternative preferred embodiment using a collection of West® Key Number Headings as the collection of classification categories The example below illustrates the relationships among the files involved in a typical research process, and provides an example of how the file-processing system accomplishes an indirect lookup using the common link of a West® Key Number Heading. In this example, the user has found a code section which bears on the research problem directly and whose primary- source item identifier is "8 USC § 1255a." He/she wants to find all the cases that discuss the issues arising in that code section. The file-processing system finds the cases linked to the code section by finding the West® Key Number Headings that are common to both: First, the file-processing system goes to the relational table that links West® Key Number Headings to one kind of primary-source item identifier (code sections) and finds all West® Key Number Headings linked to "§ 1255a," as shown in Table 15 immediately below. Second, the file-processing system goes to the relational table that links West® Key Number Headings to another kind of primary-source item identifier (case citations) and finds the primary-source item identifiers of all cases linked to the West® Key Number Headings found in the first step, as shown in Table 16 immediately below. Third, the file-processing system goes to the index to the serial file that links case citations to the locations of the corresponding text of the cases in the serial file, and finds the location of all cases identified in the second step, as shown in Table 17 immediately below. Fourth, the file-processing system goes to the locations in the serial file of cases (identified in the third step) to retrieve the three relevant passages of cases - i.e., (1) Document: "119," Field: "Opinion," Paragraph: "5; " (2) Document: "213," Field: "Opinion," Paragraph: "123;" and (3) Document: "349," Field: "Opinion," Paragraph: "66." Fifth, the computer displays the text of the cases to the user , F. File-processing-system user interface (1) Functionality illustrated in user interface The file-processing-system user interface provides the file-processing system with user directions, through menus and other interface devices, that comprise selecting, sequencing, formatting for display, full-text searching, printing, saving, annotating, scrolling, paging, expanding, collapsing, startup, navigation, and shutdown. In one preferred embodiment, the user interface is a graphical user interface (GUI) that employs windows, buttons, icons, toolbars, selection spots in text, menus, cursors, and pointers in directing the file- processing system. In response to the commands it receives from the user interface, the file-processing system processes, formats for display, and displays the specified legal content as described in "File-processing system" above. The user interface accepts the formatted displays from the file- processing system and displays them to the user on a volatile display such as a CRT. The formatted display, or other content of the system, can be further printed on paper or saved as a computer-readable file. As described in "Second primary file structure" above, the ability to view all related legal content in different, user-specified sequences is derived from the bi-directional direct links between each classification category, on the one hand, and research items and finding-tool entries, on the other hand. The system of the present invention uses such links to enable indirect linking between any research item or finding-tool entry directly linked to a common classification category, and indirect linking between any classification categories directly linked to the same research item or finding-tool entry. Since such indirect linking is invisible to the user in the GUI, to simplify the description below of the user interface, such linking is generally referred to as if it is always direct - e.g., as if a case related to a code section is directly linked to such code section, when, in fact, the only explicit links stored by the system are between the case and a classification category and the code section and the same classification category. The GUI Figures for the preferred embodiments illustrate just one among many possible approaches to presenting legal content. It is desired to emphasize that the specific displays are for the purpose of illustrating and describing the invention, and should not be considered as necessarily limiting the invention, it being understood that many modifications can be made by those skilled in the art while still practicing the invention claimed herein. For example, many variations of the file-processing- system user interface are possible. Frames in an Internet browser can be arranged in multiple layouts. Selections can be effected by buttons, icons, bars, pull-down menus, pop-up menus, dialog boxes, new windows and other interface methods that are familiar in the prior art. Still other implementation alternatives are available if the legal content is delivered on CD-ROM or as part of a proprietary on-line service such as Lexis® or Westlaw®. Because of the flexibility provided by the file structures of the present invention, publishers can readily offer the same legal content in many different layouts and with many linking variations without additional processing. However, in some cases, the functionality enabled by the file structures will not be made available in the user interface because the publisher might judge that such display will not be sufficiently useful in researching a particular practice area. For example, in the user interface described below, the display of index terms, the display of lists of primary-source item identifiers, and the enabling of hypertext links might be readily altered in the following respects: Index terms linked to a research item or finding-tool entry are only presented in this user interface in a single, alphabetical sequence. However, the file structures also make it possible to list such index terms in the order of other linked research items and finding-tool entries - e.g., the topical-index terms for the black-letter statement identifier in FIG. 118[B-13] can also be arranged in the order of regulation sections linked to the black-letter statement identifier . The list of primary-source item identifiers linked to a classification category in this user interface is only presented in a single sequence by type of primary-source item (see, e.g., FIG. 120[B-14]). In other possible embodiments, such primary-source items can also be placed in the order, for example, of forms linked to the classification category. Hypertext linking in this user interface has not been enabled for classification categories or index terms for two reasons: both types of finding tools contain relatively few direct references to target research items, and users of a service developed using the teachings of the present invention have so many obvious ways to quickly access desired research items, that also offering hypertext linking via finding tools would have introduced needless redundancy and complication. It is desired to emphasize, however, that all functionality, such as that described above, which is enabled by virtue of the file structures of the present invention, but which is not specifically illustrated in the GUI Figures, is within the scope of the present invention and is encompassed by its teachings. (2) Layout and components of sample user interface In one preferred embodiment of the present invention, the sample interface is a GUI consisting of a maximized window of an Internet browser (Internet Explorer or Netscape Navigator), as viewed in an 800 x 600 pixel display, split vertically into three frames, each of which is then split horizontally, thus: vertically by 46% left frame, 8% middle frame, 46% right frame; and horizontally 20% top / 80% bottom. The contents of the left, middle, and right frames are as follows: The left frame displays selected legal content, with buttons, as appropriate, for sequencing and navigating the materials . The middle frame contains (i) the LINK MENU for displaying, in the right frame, legal content linked to the selected item in the left frame, and (ii) an OPTIONS MENU for annotating and outputting the displayed materials in the left and right frames. The right frame displays legal content linked to a selected item in the left frame, and includes buttons, as appropriate, for sequencing and navigating the materials. Colors within this GUI are used for menus, buttons, and text as follows: Button backgrounds are blue. Black button text indicates the button is active and can be selected; white text indicates the button has been selected; red text indicates that a MENU or button is not available for selection because either the MENU has not been activated by the user, or the button represents specific materials or actions that, in the current context, might not be relevant (e.g., there are no data or links for the indicated type of item) or useful (e.g., an indicated sequence is not appropriate to the materials) . All linked legal content is highlighted (in yellow) . All selections of buttons or text (e.g., hypertext links or selections from a list of sources) are accomplished by clicking on the left mouse button. In four instances, the GUI uses slightly different terms from those used elsewhere herein to describe the invention and its preferred and alternative preferred embodiments. First, the reference in the GUI to "table-of-contents entries" is a general way of referring to the display of classification categories with their table-of-contents positions. Thus, in one preferred embodiment, "table-of-contents entries" comprise adjunct, summary, and narrow black-letter statement identifiers (also referred to collectively in the GUI as "black-letter statement identifiers") . In an alternative preferred embodiment, "table-of-contents entries" comprise West® Key Number Headings. Second, the reference to "Analysis" encompasses the particular type of secondary-source material used in a particular embodiment. In the embodiment using narrow black-letter statement identifiers, "Analysis" comprises summary black-letter statements, narrow black-letter statements, and author comments. In the embodiment using West® Key Number Headings, "Analysis" comprises case digests. Third, the reference to "index terms" comprises topical-index terms in the narrow black-letter statement identifier embodiment, and Descriptive-Word Index terms in the West® Key Number Heading embodiment. Fourth, the reference to "cite" or "citation" is the same as the description given elsewhere herein for a primary-source item identifier. (3) Use of GUI PATTERNS to organize Figures PATTERNS are a useful way of classifying research activities in the GUI - e.g., viewing the text of case or a list of index terms, selecting a case paragraph or table-of- contents entry, or displaying legal content linked to such selected item. The GUI PATTERNS can be divided in three broad categories: (i) initiating research to display and select legal content, (ii) displaying such selected legal content and making selections of its linked legal content from the activated LINK MENU, and (iii) displaying such linked legal content and selecting an item to repeat the process of (ii) above, as more fully described below: The first group of Figures, PATTERNS 1-7 (FIGS. 35-76), comprises initial research functions, whereby a user initiates research in the HOME PAGE (PATTERN 1) to display: table-of- contents entries (PATTERN 2), index terms (PATTERN 3), primary-source citations (PATTERN 4) and their corresponding text (PATTERN 5), and full-text search results — primary- and secondary-source citations (PATTERN 6) and their corresponding text (PATTERN 7) . From such displays, the user selects a table-of-contents entry, index term, primary-source item or secondary-source item to activate its LINK MENU in PATTERNS 8- 11. The second group of Figures, PATTERNS 8-11 (FIGS. 76- 101), comprises the display of a selected table-of-contents entry (PATTERN 8 - from a selection in PATTERN 2 or 12), index term (PATTERN 9 - from a selection in PATTERN 3 or 13), primary-source item (PATTERN 10 - from a selection in PATTERN 5, 7 or 15) , or secondary-source item (PATTERN 11 - from a selection in PATTERN 7 or 16) . From the activated LINK MENU in any PATTERN 8-11 Figure, the user selects linked legal content for display in PATTERNS 12-16. The third group of Figures, PATTERNS 12-16 (FIGS. 102- 142), comprises the display of legal content linked to the selected item in PATTERN 8-11 - linked table-of-contents entries (PATTERN 12), linked index terms (PATTERN 13), linked primary-source citations (PATTERN 14) and their corresponding text (PATTERN 15) , and linked secondary-source items (PATTERN 16) . Any item of such linked legal content can be selected to repeat the process described for the second group of Figures, PATTERNS 8-11, above. The relationships among the screen displays in GUI PATTERNS 1-16 described above are shown in the series of flowcharts in FIGS. 29-34. FIGS. 29-30 are for embodiments of the present invention using any collection of classification categories; FIGS. 31[B]-32[B] are for the preferred embodiment using a collection of narrow black-letter statement identifiers; FIGS. 33[W]-34[W] are for the alternative preferred embodiment using a collection of West® Key Number Headings. Within FIGS. 29-34, the different GUI PATTERNS are represented by circled numbers. 10! In the descriptions of the Figures below, examples are provided for many, but nowhere all, of the research options made possible by the present invention. Thus, an absence of examples should not be interpreted as a limitation on the present invention. In addition, to avoid redundancy, examples of a given type of functionality (e.g., hypertext linking, resequencing text, clicking a MENU button) are not repeated in every Figure to which they apply. Likewise, ellipses (...) are occasionally used to shorten displayed textual materials (e.g., cases, code sections) or lists. Finally, text- processing utilities (e.g., outputting to a file or printer, annotating research, browsing text) are not generally described unless they illustrate some specific functionality of the present invention. The numbering of the Figures under the GUI PATTERNS follows the scheme previously described in the Brief Descriptions of the Drawings, where, for example, a reference to FIG. 78[B-8] signifies that FIG. 78 illustrates a research activity within GUI PATTERN 8 for the preferred embodiment using a collection of narrow black-letter statement identifiers as the collection of classification categories. Substituting "W" for "B" indicates the alternative preferred embodiment using a collection of West® Key Number Headings. (4) Detailed description of the GUI PATTERNS and FIGURES (a) GUI PATTERN 1 (FIGS. 35-40) - INITIATE RESEARCH: HOME PAGE PATTERN 1 displays the HOME PAGE for a service created under the present invention. The HOME PAGE is accessible at system startup or by clicking the OPTION MENU "HOME" button in any other Figure in PATTERNS 2-16. The user initiates his/her research in the HOME PAGE as part of a two-step process: First, the user selects, in the PRACTICE-NAME MENU, one or more areas for research. Such selection signifies that in the subsequent research the user wants only to view legal content (primary and secondary sources, table-of-contents entries, and index terms) that is linked to the selected practice name. Second, the user makes a selection from one of the now activated research menus - the TABLE-OF-CONTENTS MENU, the INDEX MENU, the PRIMARY-SOURCE MENU, or the SEARCH MENU. The following research options are available in PATTERN 1 Figures: -1- Check one or more PRACTICE-NAME MENU [9] boxes and click the "OK" button [19] to select practice name(s). For example, go: from FIG. 35[B-1] to FIG. 36[B-1]; from FIG. 38 [W-l] to FIG. 39 [W-l] . -2- Click a TABLE-OF-CONTENTS MENU [1] button to select table-of-contents entries for display in a given sequence in PATTERN 2. For example, go: from FIG. 36[B-1] (click "Concept") to FIG. 41[B-2]; from FIG. 36[B-1] (click "Compliance") to FIG. 44[B-2]; from FIG. 36[B-1] (click "Reg §") to FIG. 47[B-2]; from FIG. 39 [W-l] (click "Key Number") to FIG. 50 [W-2] . -3- Click an INDEX MENU [2] "Letter" button to select index terms for display in PATTERN 3. For example, go: from FIG. 36[B-1] (click "A") to FIG. 55[B-3]; from FIG. 39[W-1] (click "A") to FIG. 57[W-3]. -4- Click a PRIMARY-SOURCE MENU [3] button to select an ordered list of primary-source item citations (i.e., primary- source item identifiers) for display in PATTERN 4. For example, go: from FIG. 36[B-1] (click "Reg §") to FIG. 59 [B- 4]; from FIG. 36[B-1] (click "Admin Cite") to FIG. 62[B-4]; from FIG. 39 [W-l] (click "Case Cite") to FIG. 64[W-4]. -5- Enter a SEARCH MENU [4] full-text search by entering search terms [22], checking the source materials to be searched, and clicking the "SUBMIT" button, to display a list of hits in PATTERN 6. For example, go: from FIG. 37[B-1] (enter "general and degree," check "Admin," click "SUBMIT") to FIG. 73[B-6]; from FIG. 40 [W-l] (enter "general and degree," check "Admin," click "SUBMIT") to FIG. 74 [W-6] . (b) GUI PATTERN 2 (FIGS. 41-54) - INITIATE RESEARCH: DISPLAY TABLE-OF-CONTENTS ENTRIES AND SELECT AN ENTRY PATTERN 2 displays table-of-contents entries (i) linked to the practice name(s) selected in PATTERN 1, and (ii) in the sequence selected in the TABLE-OF-CONTENTS MENU in PATTERN 1. The following research options are available in PATTERN 2 Figures : -1- Click a "LINK" button [11] adjacent to a table-of- contents entry to activate the LINK MENU [7] in PATTERN 8. For example, go: from FIG. 43[B-2] to FIG. 77[B-8]; from FIG. 46[B-2] to FIG. 78[B-8]; from FIG. 49[B-2] to FIG. 79[B-8]; from FIG. 52 [W-2] to FIG. 84[W-8]; from FIG. 5 [W-2] to FIG. 85[W-8] . -2- Click another SEQUENCE MENU [5] button to reorder the displayed table-of-contents entries. For example, go: from FIG. 41[B-2] (click "Compliance") to FIG. 44[B-2]; from FIG. 41[B-2] (click "Reg §") to FIG. 47[B-2]. -3- Click a "+" button [16] -[17] to expand the table-of- contents entries. For example, go: from FIG. 41[B-2] to FIG. 42 . B-2]; from FIG. 42[B-2] to FIG. 43[B-2]; from FIG. 44[B-2] to FIG. 45[B-2]; from FIG. 45[B-2] to FIG. 46[B-2]; from FIG. 47[B-2] to FIG. 48[B-2]; from FIG. 50 [W-2] to FIG. 51 [W-2]; from FIG. 51 [W-2] to FIG. 52 [W-2]; from FIG. 50 [W-2] to FIG. 53 [W-2]; from FIG. 53 [W-2] to FIG. 54 [W-2].: -4- Click a "-" button [18] to collapse the table-of- contents entries. For example, go: from FIG. 43[B-2] to FIG. 42[B-2]; from FIG. 42[B-2] to FIG. 41[B-2]; from FIG. 46[B-2] to FIG. 45[B-2]; from FIG. 45[B-2] to FIG. 44[B-2]; from FIG. 48[B-2] to FIG. 47[B-2]; from FIG. 52 [W-2] to FIG. 51 [W-2]; from FIG. 51 [W-2] to FIG. 50 [W-2]; from FIG. 54 [W-2] to FIG. 53 [W-2]; from FIG. 53 [W-2] to FIG. 50 [W-2]. (c) GUI PATTERN 3 (FIGS. 55-58) - INITIATE RESEARCH: DISPLAY INDEX TERMS AND SELECT A TERM PATTERN 3 displays index terms (i) linked to the practice name(s) selected in PATTERN 1, and (ii) starting from the letter selected in the INDEX MENU in PATTERN 1. The following research options are available in PATTERN 3 Figures: -1- Click an index term [26] in the index wordwheel [23], and then click the adjacent "LINK" button [11] to activate the LINK MENU [7] in PATTERN 9. For example, go: from FIG. 55[B-3] (click "Actual wage") to FIG. 56[B-3] to FIG. 88 [B-9]; from FIG. 57[W-3] (click "Adjustment of status") to FIG. 58[W-3] to FIG. 90[W-9]. (d) GUI PATTERN 4 (FIGS. 59-65) - INITIATE RESEARCH: DISPLAY LIST OF PRIMARY-SOURCE CITATIONS AND SELECT A CITATION (i) PATTERN 4 COMMENT: PATTERN 4 displays citations (i.e., primary-source item identifiers) (i) linked to the practice name(s) selected in PATTERN 1, and (ii) for the type of primary source selected in the PRIMARY-SOURCE MENU in PATTERN 1. The following research options are available in PATTERN 4 Figures: -1- Click and/or enter the primary-source item identifier [26] in wordwheel (s) [23] and [25] and/or user- input box(es) [22] and [24], and then click the "SUBMIT" button [20] to display the corresponding text in PATTERN 5. For example, go: from FIG. 59[B-4] to FIG. 60[B-4] (click [26]) to FIG. 61[B-4] (enter "655.73" in user-input box [22], click [26] "655.730(d)" and click [20] "SUBMIT") to FIG. 66 [B- 5]; from FIG. 62[B-4] to FIG. 63[B-4] (click [26], enter volume and page numbers in user-input boxes [24], and click [20] "SUBMIT") to FIG. 68 [B-5]; from FIG. 64[W-4] to FIG. 65[W-4] (click [26], enter volume and page numbers in user- input boxes [24], and click [20] "SUBMIT") to FIG. 71[W-5]. (e) GUI PATTERN 5 (FIGS. 66-72) - INITIATE RESEARCH: DISPLAY TEXT OF PRIMARY-SOURCE ITEMS AND SELECT AN ITEM PATTERN 5 displays the text of a primary-source item for the primary-source item identifier selected in PATTERN 4. The following research options are available in PATTERN 5 Figures: -1- Click a "LINK" button [11] adjacent to the text of a primary-source item to activate the LINK MENU [7] in PATTERN 10. For example, go: from FIG. 66 [B-5] to FIG. 92[B-10]; from FIG. 68 [B-5] to FIG. 93[B-10]; from FIG. 71[W-5] to FIG. 95 [W- 10]; from FIG. 72[W-5] to FIG. 96[W-10]. -2- Click a reference (hypertext link) [30] to another research item to display its text. For example, go: from FIG. 68 [B-5] to FIG. 69 [B-5]; from FIG. 131[B-15] to FIG. 67 [B-5]. (f) GUI PATTERN 6 (FIGS. 73-74) - INITIATE RESEARCH: DISPLAY LIST OF FULL-TEXT SEARCH RESULT CITATIONS AND SELECT A CITATION PATTERN 6 displays citations (i.e., primary or secondary- source item identifiers) of the primary- and secondary-source items that satisfy the search request entered in PATTERN 1. The following research options are available in PATTERN 6 Figures : -1- Click the primary- or secondary-source item identifier [31] in the list of hits from the full-text search to display the corresponding text in PATTERN 7. For example, go: from FIG. 73[B-6] to FIG. 75[B-7]; from FIG. 74 [W-6] to FIG. 76[W-7] . (g) GUI PATTERN 7 (FIGS. 75-76) - INITIATE RESEARCH: DISPLAY TEXT OF FULL-TEXT SEARCH RESULTS AND SELECT AN ITEM PATTERN 7 displays the text of a primary- or secondary- source item for the identifier selected in PATTERN 6. The following research options are available in PATTERN 7 Figures: -1- Click a "LINK" button [11] adjacent to the text of a primary- or secondary-source item to activate the LINK MENU [7] in PATTERN 10 (for primary sources) or PATTERN 11 (for secondary sources). For example, go: from FIG. 75[B-7] to FIG. 93[B-10] . -2- Click a Search-Results Navigation Menu button [10] to move to other hits. -3- Click a reference (hypertext link) to another research item to display its text in PATTERN 5. (h) GUI PATTERN 8 (FIGS. 77-87) - DISPLAY ACTIVATED LINK MENU FOR A TABLE-OF- CONTENTS ENTRY AND SELECT ITS LINKED LEGAL CONTENT PATTERN 8 displays the table-of-contents entry selected in PATTERN 2 or PATTERN 12 and its activated LINK MENU. The following research options are available in PATTERN 8 Figures: -1- Click the LINK MENU [7] buttons to display, with respect to the selected table-of-contents entry, its linked legal content in PATTERN 13 (index terms) , PATTERN 14 (primary-source items), or PATTERN 16 (secondary-source items). For example, go: from FIG. 82[B-8] (click "INDEX TERMS") to FIG. 118[B-13]; from FIG. 82[B-8] (click "ALL PRIMARY SOURCES") to FIG. 120[B-14] or from FIG. 86[W-8] (click "Cases") to FIG. 123[W-14]; from FIG. 86[W-8] (click "ANALYSIS") to FIGS. 138 [W-16] -139 [W-16] . -2- Click another SEQUENCE MENU [5] button to reorder the displayed table-of-contents entries. For example, go: from FIG. 82[B-8] (click "Reg §") to FIG. 83[B-8]. -3- Click another "LINK" button [11] to activate the LINK MENU [7] for a different table-of-contents entry. For example, go: from FIG. 80[B-8] to FIG. 81[B-8]. -4- Click the "ALL" button [15] to redisplay the table- of-contents entries as part of all table-of-contents entries linked to the selected practice name. -5- Click a "+" button [16] -[17] to expand, or "-" button [18] to collapse, the table-of-contents entries. (j) GUI PATTERN 9 (FIGS. 88-91) - DISPLAY ACTIVATED LINK MENU FOR AN INDEX TERM AND SELECT ITS LINKED LEGAL CONTENT PATTERN 9 displays the index term selected in PATTERN 3 or PATTERN 13 and its activated LINK MENU. The following research options are available in PATTERN 9 Figures: -1- Click the LINK MENU [7] buttons to display, with respect to the selected index term, its linked legal content in PATTERN 12 (table-of-contents entries), PATTERN 13 (other index terms), PATTERN 14 (primary-source items), or PATTERN 16 (secondary-source items) . For example, go: from FIG. 88 [B-9] (click "TC ENTRIES") to FIG. 102 [B-12] or from FIG. 90[W-9] (click "TC ENTRIES") to FIG. 108 [W-12]; from FIG. 88 [B-9] (click "ANALYSIS") to FIGS. 132 [B-16] -135 [B-16] . -2- Click another "LINK" button [11] to activate the LINK MENU [7] for a different index term. (k) GUI PATTERN 10 (FIGS. 92-96) - DISPLAY ACTIVATED LINK MENU FOR A PRIMARY-SOURCE ITEM AND SELECT ITS LINKED LEGAL CONTENT PATTERN 10 displays the primary-source item selected in PATTERN 5, PATTERN 7, or PATTERN 15 and its activated LINK MENU. The following research options are available in PATTERN 10 Figures: -1- Click the LINK MENU [7] buttons to display, with respect to the selected primary-source item, its linked legal content in PATTERN 12 (table-of-contents entries), PATTERN 13 (index terms), PATTERN 14 (other primary-source items), or PATTERN 16 (secondary-source items). For example, go: from FIG. 92[B-10] (click "TC ENTRIES") to FIG. 112 [B-12] or from FIG. 93[B-10] (click "TC ENTRIES") to FIG. 115 [B-12]; from FIG. 96[W-10] (click "INDEX TERMS") to FIG. 119[W-13]; from FIG. 92[B-10] (click "Code") to FIG. 121[B-14], or from FIG. 92[B-10] (click "Forms") to FIG. 125[B-14], or from FIG. 96 [W- 10] (click "Code") to FIG. 122 [W-14], or from FIG. 96[W-10] (click "Cases") to FIG. 124 [W-14]; from FIG. 96[W-10] (click "ANALYSIS") to FIG. 142 [W-16]. -2- Click another "LINK" button [11] to activate the LINK MENU [7] for a different primary-source item. -3- Click a reference (hypertext link) [30] to another research item to display its text in PATTERN 5. (1) GUI PATTERN 11 (FIGS. 97-101) - DISPLAY ACTIVATED LINK MENU FOR A SECONDARY-SOURCE ITEM AND SELECT ITS LINKED LEGAL CONTENT PATTERN 11 displays the secondary-source item selected in PATTERN 7 or PATTERN 16 and its activated LINK MENU. The following research options are available in PATTERN 11 Figures : -1- Click the LINK MENU [7] buttons to display, with respect to the selected secondary-source item, its linked legal content in PATTERN 12 (table-of-contents entries), PATTERN 13 (index terms), PATTERN 14 (primary-source items), or PATTERN 16 (other secondary-source items). -2- Click another SEQUENCE MENU [5] button to reorder the displayed secondary-source items. -3- Click another "LINK" button [11] to activate the LINK MENU [7] for a different secondary-source item. -4- Click a reference (hypertext link) [30] to another research item to display its text in PATTERN 5. (m) GUI PATTERN 12 (FIGS. 102-117) - DISPLAY LINKED TABLE-OF-CONTENTS ENTRIES AND SELECT AN ENTRY PATTERN 12 displays (i) in the left frame: an index term (from PATTERN 9), primary-source item (from PATTERN 10), or secondary-source item (from PATTERN 11), and (ii) in the right frame: the linked table-of-contents entries that were selected using the LINK MENU "TC ENTRIES" button in PATTERNS 9-11. All the research options available for the selected legal content in PATTERNS 9-11 are also available, as relevant, in PATTERN 12 Figures. In addition, in PATTERN 12 the user may: -1- Click a "LINK" button [11] -[12] adjacent to a table- of-contents entry (in the right frame) to activate a new LINK MENU [7] for the selected entry in PATTERN 8. For example, go: from FIG. 102 [B-12] (click [11]) to FIG. 80[B-8]; from FIG. 102[B-12] (click [12]) to FIG. 81[B-8]; from FIG. 108 [W-12] (click [11]) to FIG. 86[W-8]; from FIG. 112 [B-12] (click [11]) to FIG. 82[B-8]; from FIG. 117 [W-12] (click [11]) to FIG. 87 [W-8] . -2- Click another SEQUENCE MENU [6] button to reorder the displayed table-of-contents entries. For example, go: from FIG. 102 [B-12] (click "Reg §") to FIG. 107 [B-12]; from FIG. 112 [B-12] (click "Reg §") to FIG. 113 [B-12]; from FIG. 113 [B- 12] (click "Form No.") to FIG. 114 [B-12]. -3- Click the "ALL" button [15] to redisplay the table- of-contents entries as part of all table-of-contents entries linked to the selected practice name (i.e., of "Immigration"). For example, go: from FIG. 102 [B-12] to FIGS. 103 [B-12] -106 [B- 12]; from FIG. 108 [W-12] to FIGS. 109 [W-12 ] -111 [W-12 ] . (n) GUI PATTERN 13 (FIGS. 118-119) - DISPLAY LINKED INDEX TERMS AND SELECT A TERM PATTERN 13 displays (i) in the left frame: a table-of- contents entry (from PATTERN 8), index term (from PATTERN 9), primary-source item (from PATTERN 10), or secondary-source item (from PATTERN 11), and (ii) in the right frame: the linked index terms that were selected using the LINK MENU "INDEX TERMS" button in PATTERNS 8-11. All the research options available for the selected legal content in PATTERNS 8-11 are also available, as relevant, in PATTERN 13 Figures. In addition, in PATTERN 13 the user may: -1- Click a "LINK" button [11] adjacent to an index term (in the right frame) to activate a new LINK MENU [7] for the selected term in PATTERN 9. For example, go: from FIG. 118 [B- 13] to FIG. 89[B-9]; from FIG. 119[W-13] to FIG. 91 [W-9] . (o) GUI PATTERN 14 (FIGS. 120-125) - DISPLAY LINKED PRIMARY-SOURCE CITATIONS AND SELECT A CITATION PATTERN 14 displays (i) in the left frame: a table-of- contents entry (from PATTERN 8), index term (from PATTERN 9), primary-source item (from PATTERN 10), or secondary-source item (from PATTERN 11), and (ii) in the right frame: the linked primary-source item identifiers that were selected using the LINK MENU "ALL PRIMARY SOURCES," "Code," "Regs," "Cases," "Admin," "Rules," or "Forms" button in PATTERNS 8-11. All the research options available for the selected legal content in PATTERNS 8-11 are also available, as relevant, in PATTERN 14 Figures. In addition, in PATTERN 14 the user may: -1- Click a primary-source item identifier [31] -[34] to display its corresponding text in PATTERN 15. For example, go: from FIG. 120[B-14] (click [33]) to FIG. 129[B-15]; from FIG. 121[B-14] (click [31]) to FIGS. 126 [B-15] -127 [B-15] ; from FIG. 123 [W-14] (click [31]) to FIG. 128[W-15]; from FIG. 125[B-14] (click [33]) to FIGS. 130 [B-15] -131 [B-15] . (p) GUI PATTERN 15 (FIGS. 126-131) - DISPLAY TEXT OF LINKED PRIMARY-SOURCE ITEM AND SELECT AN ITEM PATTERN 15 displays (i) in the left frame: a table-of- contents entry (from PATTERN 8), index term (from PATTERN 9), primary-source item (from PATTERN 10), or secondary-source item (from PATTERN 11), and (ii) in the right frame: the text of a linked primary-source item that was selected by clicking a primary-source item identifier in PATTERN 14. All the research options available for the selected legal content in PATTERNS 8-11 are also available, as relevant, in PATTERN 15 Figures. In addition, in PATTERN 15 the user may: -1- Click a "LINK" button [11] adjacent to the text of a primary-source item (in the right frame) to activate a new LINK MENU [7] for the selected item in PATTERN 10. For example, go: from FIG. 129 [B-15] to FIG. 94[B-10]. -2- Click one of the Navigation Menu [10] buttons to navigate to the next or prior sub-unit of displayed text that is linked to the selected research item or finding-tool entry in the left frame. -3- Click a reference (hypertext link) [30] to another research item to display its text in PATTERN 5. For example, go: from FIG. 131 [B-15] to FIG. 67 [B-5] . (q) GUI PATTERN 16 (FIGS. 132-142) - DISPLAY LINKED SECONDARY-SOURCE ITEM AND SELECT AN ITEM PATTERN 16 displays (i) in the left frame: a table-of- contents entry (from PATTERN 8), index term (from PATTERN 9), primary-source item (from PATTERN 10), or secondary-source item (from PATTERN 11), and (ii) in the right frame: the linked secondary-source items that were selected using the LINK MENU "ANALYSIS" button in PATTERNS 8-11. All the research options available for the selected legal content in PATTERNS 8-11 are also available, as relevant, in PATTERN 16 Figures. In addition, in PATTERN 16 the user may: -1- Click a "LINK" button [11] adjacent to the text of a secondary-source item (in the right frame) to activate a new LINK MENU [7] for the selected item in PATTERN 11. For example, go: from FIG. 132 [B-16] to FIG. 97[B-11]; from FIG. 136[B-16] to FIG. 98[B-11]; from FIG. 142[W-16] to FIG. 99 [W- 11]; from FIG. 141 [W-16] to FIGS. 100 [W-ll ] -101 [W-ll] . -2- Click another SEQUENCE MENU [6] button to reorder the displayed secondary-source items. For example, go: from FIG. 132 [B-16] (click "Reg §") to FIGS. 136 [B-16] -137 [B-16] ; from FIG. 138 [W-16] (click "Code §") to FIGS. 140 [W-16] -141 [W- 16] . -3- Click a reference (hypertext link) [30] to another research item to display its text in PATTERN 5.

Claims: V. CLAIMS WE CLAIM: 1. A computerized research system for processing and displaying scientific, technical, academic, or professional content, comprising: a. computer-readable scientific, technical, academic, or professional content, wherein said content comprises, in computer-readable form: i. a collection of classification categories, ii. source items and source-item identifiers, iii. (sub) discipline names, index terms, tables of source-item identifiers, and table-of-contents entries ; b. a file-building system; c. file structures which: i. retrievably store said content, ii. directly link said content, iii. enable indirect linking of said content, and iv. enable full text searching of said content; d. a file-processing system; and e. a file-processing-system user interface. 2. The system of claim 1, wherein said file-building system builds files and supporting indices comprising a first primary file structure, a second primary file structure, and ancillary file structures. 3. The system of claim 2, wherein said file-building system builds said first primary file structure from source items of scientific, technical, academic, or professional (sub) disciplines . 4. The system of claim 3, wherein said first primary file structure : a. retrievably stores source items; and b. enables full-text searching of source items. 5. The system of claim 4, wherein said first primary file structure further supports hypertext linking. 6. The system of claim 3, wherein said first primary file structure comprises: a. a serial file of displayable text; b. an inverted index of words with information about each word's position in the serial file; c. an index of source-item identifiers with pointers to the position of each such item in the serial file; and d. an index of hypertext links for cross-references in text, comprising, for each cross-reference, i. the item identifier of the citing document and the location of the cross-reference in the serial file of the citing document, and ii. the item identifier of the cited document and the location of the cross-reference in the text of the cited document. 7. The system of claim 2, wherein said file-building system builds said second primary file structure by: a. deriving, from the scientific, technical, academic, or professional content, each two-member set of: i. a classification category, and ii. a source-item identifier, (sub) discipline name, index term, or table-of-contents position; b. entering said two-member sets into a file structure having relational capability; and c. building the indices thereto to permit rapid finding of direct and indirect links. 8. The system of claim 2, wherein said second primary file structure provides a bi-directional direct linking: a. in one direction from a classification category to a source-item identifier, a (sub) discipline name, or an index term; and b. in the opposite direction from a source-item identifier, a (sub) discipline name, or an index term to a classification category. 9. The system of claim 8, wherein said second primary file structure enables: a. a first indirect linking, derived from said bidirectional direct linking, between: i. a source-item identifier, a (sub) discipline name, or an index term, and ii. another source-item identifier, (sub) discipline name, or index term, having a common classification category; b. a second indirect linking, derived from said bi- directional direct linking, between: i. a classification category, and ii. another classification category, having a common source-item identifier, a (sub) discipline name, or an index term; and c. the chaining of said direct linking, said first indirect linking, and said second indirect linking in any and all permutations and combinations. 10. The system of claim 2, wherein said ancillary file structures enable, among other things, the building of menus of: a. (sub) discipline names; b. table-of-contents sequences for classification categories; c. categories of index terms; d. types of sources; and e. full-text-search options. 11. The system of claim 1, wherein said file-processing system in response to externally specified commands: a. processes specified (sub) discipline content; b. formats said processed specified (sub) discipline content for display; and c. displays said formatted processed specified (sub) discipline content. 12. The system of claim 11, wherein said processing comprises finding direct links and building indirect links. 13. The system of claim 12, wherein directly and indirectly linked (sub) discipline content is formatted and displayed. 14. The system of claim 11, wherein said processing comprises performing full-text searches. 15. The system of claim 11, wherein said processing comprises finding hypertext links. 16. The system of claim 11, wherein said processing comprises: a. selecting classification categories, and b. sequencing said selected classification categories in a specified table-of-contents sequence. 17. The system of claim 11, wherein said processing comprises building a link menu for said specified (sub) discipline content . 18. The system of claim 11, wherein said processing comprises : a. selecting source-item identifiers of a given type; b. sequencing said item identifiers; and c. building a list of said selected and sequenced item identifiers . 19. The system of claim 11, wherein said processing further comprises building menus of: a. (sub) discipline names; b. table-of-contents sequences for classification categories; c. categories of index terms; d. types of sources; and e. full-text-search options. 20. The system of claim 11, wherein said file-processing system, in response to externally specified commands: a. performs printing and saving to a permanent file; and b. performs miscellaneous scrolling, paging, expanding, collapsing, startup, navigation, annotating, and shutdown functions. 21. The system of claim 11, wherein said file-processing system m response to externally specified commands: a. processes (sub) discipline content, namely: l. finds specified direct links and builds indirect links, ii. performs full-text searches, in. finds hypertext links, iv. selects classification categories and sequences said selected classification categories in a specified table-of-contents sequence, v. builds link menus for specified (sub) discipline content, vi. selects source-item identifiers of a given type, sequences said item identifiers, and builds a list of said selected and sequenced item identifiers, vii. builds menus of (sub) discipline names, table- of-contents sequences for classification categories, categories of index terms, types of sources, and/or full-text-search options; b. formats said processed ( sub) discipline content for display, printing, saving to a file, or other use; c. displays said formatted processed (sub) discipline content; d. performs miscellaneous scrolling, paging, expanding, collapsing, startup, navigation, and shutdown functions . 22. The system of claim 11, wherein said user interface provides the file-processing system with said externally specified commands. 23. The system of claim 22, wherein said user interface accepts said formatted processed legal content and displays same to the user on a volatile display such as a CRT. 24. The system of claim 22, wherein said formatted processed specified ( sub) discipline content is printed on paper or saved as a computer-readable file. 25. The system of claim 22, wherein said user interface provides the user with menus for selecting directions for the file-processmg system. 26. The system of claim 25, wherein said user selectable directions comprise: selecting, sequencing, formatting for display, full-text searching, hypertext linking, printing, saving, annotating, scrolling, paging, expanding, collapsing, startup, navigation, and shutdown. 27. The system of claim 26, wherein said user interface is a graphical user interface that employs windows, buttons, icons, toolbars, selection spots in text, menus, cursors, and pointers in directing the file-processmg system. 28. The computerized research system of claim 1, wherein said system is implemented on processing devices, storage devices, and networks that are located m a single location or distributed over multiple locations. 29. The system of claim 28, wherein: a. said processing devices comprise mainframe computers, mini-computers, and/or personal computers; b. said storage devices comprise magnetic storage devices and/or optical storage devices; and c. said networks comprise private communications networks, public and/or private Internets, and/or any other public network. 30. A computerized research system for processing and displaying computer-readable (sub) discipline content, comprising: a. (sub) discipline content, wherein said ( sub) discipline content comprises: i. a collection of classification categories, ii. a first source type and associated source items and source-item identifiers, and iii. a second source type and associated source items and source-item identifiers; b. a file-building system; c. file structures which: i. retrievably store (sub) discipline content, ii. directly link (sub) discipline content, and iii. enable indirect linking of (sub) discipline content; d. a file-processing system; and e. a file-processing-system user interface. 31. A computerized research system for processing and displaying computer-readable (sub) discipline content, comprising: a. ( sub) discipline content, wherein said (sub) discipline content comprises a collection of classification categories, source items, and index terms; b. a file-building system; c. file structures which: i. retrievably store (sub) discipline content, ii. directly link ( sub) discipline content, and iii. enable indirect linking of (sub) discipline content; d. a file-processing system; and e. a file-processing-system user interface. 32. A computerized method for processing ( sub) discipline content files in response to externally specified commands, the method comprising: a. finding specified direct links and building indirect links between classification categories and other (sub) discipline content; b. formatting said directly and indirectly linked (sub) discipline content for display, printing, saving to a file, or other use; c. displaying, printing, saving to a file, or performing said other use (with respect to) said formatted, directly and indirectly linked, ( sub) discipline content. 33. A computerized research system for processing and displaying legal content, comprising: a. legal content, wherein said legal content comprises, in computer-readable form: i. a collection of classification categories, ii. primary-source items, primary-source item identifiers, secondary-source items and secondary-source item identifiers, and iii. practice names, topical-index terms, tables of primary-source item identifiers, and tables of contents ; b. a file-building system wherein said file-building system builds files and supporting indices comprising a first primary file structure, a second primary file structure and ancillary file structures; c. wherein said first primary file structure retrievably stores legal content; d. wherein said second primary file structure provides a bi-directional direct linking, i. in one direction from a classification category to a primary-source item identifier, a secondary-source item identifier, a practice name, or a topical-index term, and ii. in the opposite direction from a primary-source item identifier, a secondary-source item identifier, a practice name, or a topical-index term to a classification category; e. wherein said ancillary file structure enables, among other things, the building of menus of: i. practice names, ii. table-of-contents sequences for classification categories, iii. categories of topical-index terms, and iv. types of primary source; f. a file-processing system, which in response to externally specified commands: i. processes specified legal content, ii. formats said processed specified legal content for display, iii. displays said formatted processed specified legal content; and g. a file-processing-system user interface, which provides the file-processing system with said externally specified commands. 34. The system of claim 33, wherein: a. said collection of classification categories comprises a collection of narrow black-letter statement identifiers; b. said secondary-source items comprise narrow black- letter statements, summary black-letter statements and author comments; and c. said secondary-source item identifiers comprise narrow black-letter statement identifiers, summary black-letter statement identifiers, and author- comment identifiers. 35. The system of claim 33, wherein: a. said collection of classification categories are derived from the West Key Number System®, b. said secondary-source items comprise West's case digests; and c. said secondary-source item identifiers comprise West's case-digest identifiers. 36. The system of claim 33, wherein: a. said collection of classification categories are derived from treatise tables of contents; b. said secondary-source items comprise the treatise text; and c. said secondary-source item identifiers comprise treatise-text identifiers. 37. The system of claim 33, wherein said first primary file structure additionally: a. enables full-text searching of legal content; and b. supports hypertext linking. 38. The system of claim 33, wherein said second primary file structure enables: a. a first indirect linking, derived from said bidirectional direct linking, between: l. a primary-source item identifier, a secondary- source item identifier, a practice name, or a topical-mdex term, and ii. another primary-source item identifier, secondary-source item identifier, practice name, or topical-mdex term, having a common classification category; b. a second indirect linking, derived from said bidirectional direct linking, between: l. a classification category, and ii. another classification category, having a common primary-source item identifier, secondary-source item identifier, practice name, or topical-index term; c. the chaining of said direct linking, said first indirect linking, and said second indirect linking in any and all permutations and combinations. 39. The system of claim 33, wherein said ancillary file structure further enables the building of menus of full- text-search options. 40. A computerized research system for processing and displaying legal content, comprising: a. legal content, wherein said legal content comprises, in computer-readable form: i. a collection of narrow black-letter statement identifiers, ii. primary-source items and primary-source item identifiers, iii. narrow black-letter statements, summary black- letter statements, author comments, narrow black-letter statement identifiers, summary black-letter statement identifiers, and author- comment identifiers, and iv. practice names, topical-index terms, tables of primary-source item identifiers, and table-of- contents entries; b. a file-building system; c. file structures which: i. retrievably store legal content, ii. directly link legal content, iii. enable indirect linking of legal content, and iv. enable full text searching of legal content; d. a file-processing system; and e. a file-processing-system user interface. 41. The system of claim 40, wherein said file-building system builds files and supporting indices comprising a first primary file structure, a second primary file structure, and ancillary file structures. 42. The system of claim 41, wherein said file-building system builds said first primary file structure from primary- source items, primary-source item identifiers, narrow black-letter statements, summary black-letter statements, author comments, narrow black-letter statement identifiers, summary black-letter statement identifiers, and author-comment identifiers. 43. The system of claim 42, wherein said first primary file structure : a. retrievably stores legal content; and b. enables full-text searching of legal content. 44. The system of claim 43, wherein said first primary file structure further supports hypertext linking. 45. The system of claim 42, wherein said first primary file structure comprises: a. a serial file of displayable text; b. an inverted index of words with information about each word's position in the serial file; c. an index of primary-source and secondary-source item identifiers with pointers to the position of each such item in the serial file; and d. an index of hypertext links for cross-references in text, comprising, for each cross-reference, i. the item identifier of the citing document and the location of the cross-reference in the serial file of the citing document, and ii. the item identifier of the cited document and the location of the cross-reference in the text of the cited document. 46. The system of claim 41, wherein said file-building system builds said second primary file structure by: a. deriving, from the legal content, each two-member set of: i. narrow black-letter statement identifier, and ii. practice name, topical-index term, table-of- contents position, primary-source item identifier, summary black-letter statement identifier, or author-comment identifier; b. entering said two-member sets into a file structure having relational capability; and c. building the indices thereto to permit rapid finding of direct and indirect links. 47. The system of claim 41, wherein said second primary file structure provides a bi-directional direct linking: a. in one direction from a narrow black-letter statement identifier to a primary-source item identifier, a summary black-letter statement identifier, an author-comment identifier, a practice name, or a topical-index term; and b. in the opposite direction from a primary-source item identifier, a summary black-letter statement identifier, an author-comment identifier, a practice name, or a topical-index term to a narrow black- letter statement identifier. 48. The system of claim 47, wherein said second primary file structure enables: a. a first indirect linking, derived from said bi- directional direct linking, between: i. a primary-source item identifier, a summary black-letter statement identifier, an author- comment identifier, a practice name, or a topical-index term, and ii. another primary-source item identifier, summary black-letter statement identifier, author- comment identifier, practice name, or topical- index term, having a common narrow black-letter statement identifier; b. a second indirect linking, derived from said bidirectional direct linking, between: l. a narrow black-letter statement identifier, and ii. another narrow black-letter statement identifier, having a common primary-source item identifier, summary black-letter statement identifier, author- comment identifier, practice name, or topical-mdex term; and c. the chaining of said direct linking, said first indirect linking, and said second indirect linking m any and all permutations and combinations. 49. The system of claim 41, wherein said ancillary file structures enable, among other things, the building of menus of: a. practice names; b. table-of-contents sequences for narrow black-letter statement identifiers; c. categories of topical-mdex terms; d. types of primary source; and e. full-text-search options. 50. The system of claim 40, wherein said file-processmg system m response to externally specified commands: a. processes specified legal content; b. formats said processed specified legal content for display; and c. displays said formatted processed specified legal content . 51. The system of claim 50, wherein said processing comprises finding direct links and building indirect links. 52. The system of claim 51, wherein directly and indirectly linked legal content is formatted and displayed. 53. The system of claim 50, wherein said processing comprises performing full-text searches. 54. The system of claim 50, wherein said processing comprises finding hypertext links. 55. The system of claim 50, wherein said processing comprises : a. selecting narrow black-letter statement identifiers; and b. sequencing said selected narrow black-letter statement identifiers in a specified table-of- contents sequence. 56. The system of claim 50, wherein said processing comprises building a link menu for said specified legal content. 57. The system of claim 50, wherein said processing comprises: a. selecting primary-source item identifiers of a given type; b. sequencing said item identifiers; and c. building a list of said selected and sequenced item identifiers. 58. The system of claim 50, wherein said processing further comprises building menus of: a. practice names; b. table-of-contents sequences for narrow black-letter statement identifiers; c. categories of topical-index terms; d. types of primary-source; and e. full-text-search options. 59. The system of claim 50, wherein said file-processing system, in response to externally specified commands: a. performs printing and saving to a permanent file; and b. performs miscellaneous scrolling, paging, expanding, collapsing, startup, navigation, annotating, and shutdown functions. 60. The system of claim 50, wherein said file-processing system in response to externally specified commands: a. processes legal content, namely: i. finds specified direct links and builds indirect links, ii. performs full-text searches, iii. finds hypertext links, iv. selects narrow black-letter statement identifiers and sequences said selected narrow black-letter statement identifiers in a specified table-of-contents sequence, v. builds link menus for specified legal content, vi . selects primary-source item identifiers of a given type, sequences said item identifiers, and builds a list of said selected and sequenced item identifiers, vii. builds menus of practice names, table-of- contents sequences for narrow black-letter statement identifiers, categories of topical- index terms, types of primary-source, and/or full-text-search options; b. formats said processed legal content for display, printing, saving to a file, or other use; c. displays said formatted processed legal content; d. performs miscellaneous scrolling, paging, expanding, collapsing, startup, navigation, and shutdown functions . 61. The system of claim 50, wherein said user interface provides the file-processing system with said externally specified commands. 62. The system of claim 61, wherein said user interface accepts said formatted processed legal content and displays same to the user on a volatile display such as a CRT. 63. The system of claim 61, wherein said formatted processed specified legal content is printed on paper or saved as a computer-readable file. 64. The system of claim 61, wherein said user interface provides the user with menus for selecting directions for the file-processmg system. 65. The system of claim 64, wherein said user selectable directions comprise: selecting, sequencing, formatting for display, full-text searching, hypertext linking, printing, saving, annotating, scrolling, paging, expanding, collapsing, startup, navigation, and shutdown. 66. The system of claim 65, wherein said user interface is a graphical user interface that employs windows, buttons, icons, toolbars, selection spots m text, menus, cursors, and pointers m directing the file-processing system. 67. The computerized research system of claim 40, wherein said system is implemented on processing devices, storage devices, and networks that are located m a single location or distributed over multiple locations. 68. The system of claim 67, wherein: a. said processing devices comprise mainframe computers, mini-computers, and/or personal computers; b. said storage devices comprise magnetic storage devices and/or optical storage devices; and c. said networks comprise private communications networks, public and/or private Internets, and/or any other public network. 69. A computerized method for processing legal content files in response to externally specified commands, the method comprising : a. finding specified direct links and building indirect links between narrow black-letter statement identifiers and other legal content; b. formatting said directly and indirectly linked legal content for display, printing, saving to a file, or other use; c. displaying, printing, saving to a file, or performing said other use (with respect to) said formatted, directly and indirectly linked, legal content . 70. A computerized research system for processing and displaying legal content, comprising: a. legal content, wherein said legal content comprises, m computer-readable form: l. a collection of West® Key Number Headings, ii. primary-source items and primary-source item identifiers, in. West's case digests and case-digest identifiers, and iv. practice names, Descriptive-Word Index terms and identification of the case digests to which they refer, tables of primary-source item identifiers, and table (s) of contents; b. a file-buildmg system; c. file structures which: l. retrievably store legal content, ii. directly link legal content, in. enable indirect linking of legal content, and iv. enable full-text searching of legal content; d. a file-processmg system; and e. a flle-processmg-system user interface. 71. The system of claim 70, wherein said West® Key Number Headings further comprise: a. a topic name; b. a key number; and c. a key line. 72. The system of claim 70, wherein said f le-buildmg system builds files and supporting indices comprising a first primary file structure, a second primary file structure, and ancillary file structures. 73. The system of claim 72, wherein said file-buildmg system builds said first primary file structure from primary- source items, primary-source item identifiers, West's case digests, and West's case-digest identifiers 74. The system of claim 73, wherein said first primary file structure : a. retrievably stores legal content; and b. enables full-text searching of legal content. 75. The system of claim 74, wherein said first primary file structure further supports hypertext linking. 76. The system of claim 73, wherein said first primary file structure comprises: a. a serial file of displayable text; b. an inverted index of words with information about each word's position in the serial file; c. an index of primary-source item identifiers and case-digest identifiers with pointers to the position of each such item in the serial file; and d. an index of hypertext links for cross-references m text, comprising, for each cross-reference, l. the item identifier of the citing document and the location of the cross-reference m the serial file of the citing document, and ii. the item identifier of the cited document and the location of the cross-reference in the text of the cited document. 77. The system of claim 72, wherein said file-buildmg system builds said second primary file structure by: a. deriving, from the legal content, each two-member set of: l. West® Key Number Heading, and ii. practice name, West Descriptive-Word Index term, table-of-contents position, primary- source item identifier, or case-digest identifier; b. entering said two-member sets into a file structure having relational capability; and c. building the indices thereto to permit rapid finding of direct and indirect links. 78. The system of claim 72, wherein said second primary file structure provides a bi-directional direct linking: a. in one direction from West® Key Number Heading to a primary-source item identifier, a case-digest identifier, a practice name, or West Descriptive- Word Index term; and b. in the opposite direction from a primary-source item identifier, a case-digest identifier, a practice name, or a West Descriptive-Word Index term to a West® Key Number Heading. 79. The system of claim 78, wherein said second primary file structure enables: a. a first indirect linking, derived from said bi- directional direct linking, between: i. a primary-source item identifier, a case-digest identifier, a practice name, or a West Descriptive-Word Index term, and ii. another primary-source item identifier, case- digest identifier, practice name, or West Descriptive-Word Index term, having a common West® Key Number Heading; b. a second indirect linking, derived from said bi- directional direct linking, between: i. a West® Key Number Heading, and ii. another West® Key Number Heading, having a common primary-source item identifier, case-digest identifier, practice name, or West Descriptive-Word Index term; and c. the chaining of said direct linking, said first indirect linking, and said second indirect linking in any and all permutations and combinations. 80. The system of claim 72, wherein said ancillary file structures enable, among other things, the building of menus of: a. practice names; b. categories of West Descriptive-Word Index terms; c. types of primary source; and d. full-text-search options. 81. The system of claim 70, wherein said file-processing system in response to externally specified commands: a. processes specified legal content; b. formats said processed specified legal content for display; and c. displays said formatted processed specified legal content. 82. The system of claim 81, wherein said processing comprises finding direct links and building indirect links. 83. The system of claim 82, wherein directly and indirectly linked legal content is formatted and displayed. 84. The system of claim 81, wherein said processing comprises performing full-text searches. 85. The system of claim 81, wherein said processing comprises finding hypertext links. 86. The system of claim 81, wherein said processing comprises building a link menu for said specified legal content. 87. The system of claim 81, wherein said processing comprises : a. selecting primary-source item identifiers of a given type; b. sequencing said item identifiers; and c. building a list of said selected and sequenced item identifiers . 88. The system of claim 81, wherein said processing further comprises building menus of: a. practice names; b. categories of West Descriptive-Word Index terms; c. types of primary-source; and d. full-text-search options. 89. The system of claim 81, wherein said file-processing system, in response to externally specified commands: a. performs printing and saving to a permanent file; and b. performs miscellaneous scrolling, paging, expanding, collapsing, startup, navigation, annotating, and shutdown functions. 90. The system of claim 81, wherein said file-processing system in response to externally specified commands: a. processes legal content, namely: ii. finds specified direct links and builds indirect links, iii. performs full-text searches, iii. finds hypertext links, iv. builds link menus for specified legal content, v. selects primary-source item identifiers of a given type, sequences said item identifiers, and builds a list of said selected and sequenced item identifiers, vi . builds menus of practice names, categories of West Descriptive-Word Index terms, types of primary-source, and/or full-text-search options ; b. formats said processed legal content for display, printing, saving to a file, or other use; c. displays said formatted processed legal content; d. performs miscellaneous scrolling, paging, expanding, collapsing, startup, navigation, and shutdown functions . 91. The system of claim 81, wherein said user interface provides the file-processing system with said externally specified commands. 92. The system of claim 91, wherein said user interface accepts said formatted processed legal content and displays same to the user on a volatile display such as a CRT. 93. The system of claim 91, wherein said formatted processed specified legal content is printed on paper or saved as a computer-readable file. 94. The system of claim 91, wherein said user interface provides the user with menus for selecting directions for the file-processing system. 95. The system of claim 94, wherein said user selectable directions comprise: selecting, sequencing, formatting for display, full-text searching, hypertext linking, printing, saving, annotating, scrolling, paging, expanding, collapsing, startup, navigation, and shutdown. 96. The system of claim 95, wherein said user interface is a graphical user interface that employs windows, buttons, icons, toolbars, selection spots in text, menus, cursors, and pointers in directing the file-processing system. 97. The computerized research system of claim 70, wherein said system is implemented on processing devices, storage devices, and networks that are located in a single location or distributed over multiple locations. 98. The system of claim 97, wherein: a. said processing devices comprise mainframe computers, mini-computers, and/or personal computers ; b. said storage devices comprise magnetic storage devices and/or optical storage devices; and c. said networks comprise private communications networks, public and/or private Internets, and/or any other public network. 99. A computerized method for processing legal content files in response to externally specified commands, the method comprising: a. finding specified direct links and building indirect links between West® Key Number Headings and other legal content; b. formatting said directly and indirectly linked legal content for display, printing, saving to a file, or other use; c. displaying, printing, saving to a file, or performing said other use (with respect to) said formatted, directly and indirectly linked, legal content . 100. A computerized research system for processing and displaying computer-readable legal content, comprising: a. legal content, wherein said legal content comprises: i. a collection of classification categories, ii . a first primary source type and associated primary-source items and primary-source item identifiers, and iii. a second primary source type and associated primary-source items and primary-source item identifiers ; b. a file-building system; c. file structures which: i. retrievably store legal content, ii. directly link legal content, and iii. enable indirect linking of legal content; d. a file-processing system; and e. a file-processing-system user interface. 101. The computerized system according to claim 100, wherein said collection of classification categories comprises narrow black-letter statement identifiers. 102. The computerized system according to claim 100, wherein said collection of classification categories comprises West® Key Number Headings. 103. The computerized system according to claim 100, wherein said collection of classification categories comprises treatise table-of-contents entries. 104. A computerized research system for processing and displaying computer-readable legal content, comprising: a. legal content, wherein said legal content comprises a collection of narrow black-letter statement identifiers, primary-source items, primary-source item identifiers, and either: author comments and author-comment identifiers, or topical-index terms; b. a file-building system; c. file structures which: i. retrievably store legal content, ii. directly link legal content, and iii. enable indirect linking of legal content; d. a file-processing system; and e. a file-processing-system user interface. 105. A computerized research system for processing and displaying computer-readable legal content, comprising: a. legal content, wherein said legal content comprises a collection of West® Key Number Headings, primary- source items, primary-source item identifiers, and either: West's case digest and case-digest identifiers, or West Descriptive-Word Index terms; b. a file-building system; c. file structures which: i. retrievably store legal content, ii. directly link legal content, and iii. enable indirect linking of legal content; d. a file-processing system; and e. a flle-processmg-system user interface. 106. A computerized research system for processing and displaying computer-readable legal content, comprising: a. legal content, wherein said legal content comprises a collection of treatise table-of-contents entries, primary-source items, primary-source item identifiers, and either: treatise text and treatise- text identifiers, or treatise index terms; b. a file-buildmg system; c. file structures which: l. retrievably store legal content, ii. directly link legal content, and in. enable indirect linking of legal content; d. a file-processmg system; and e. a file-processmg-system user interface. 107. A computerized research system for processing and displaying computer-readable legal content, comprising: a. legal content, wherein said legal content comprises a collection of narrow black-letter statement identifiers, author comments, author-comment identifiers, and topical-mdex terms; b. a file-buildmg system; c. file structures which: l. retrievably store legal content, ii. directly link legal content, and in. enable indirect linking of legal content; d. a file-processmg system; and e. a file-processmg-system user interface. 108. A computerized research system for processing and displaying computer-readable legal content, comprising: a. legal content, wherein said legal content comprises a collection of West® Key Number Headings, West's case digest, case-digest identifiers, and West Descriptive-Word Index terms; b. a file-building system; c. file structures which: I. retrievably store legal content, II. directly link legal content, and in. enable indirect linking of legal content; d. a file-processmg system; and e. a file-processmg-system user interface. 109. A computerized research system for processing and displaying computer-readable legal content, comprising: a. legal content, wherein said legal content comprises a collection of treatise table-of-contents entries, treatise text, treatise-text identifiers, and treatise-mdex terms; b. a file-buildmg system; c. file structures which: l. retrievably store legal content, ii. directly link legal content, and in. enable indirect linking of legal content; d. a file-processing system; and e. a file-processmg-system user interface. 110. A computerized method of authoring and editing computer readable legal content for use in a computerized research system, wherein said method comprises a. writing narrow black-letter statements and narrow black-letter statement identifiers, summary black- letter statements and summary black-letter statement identifiers, and topical-mdex terms, and designating them as such m a computer-recognizable manner; and b. assigning to each narrow black-letter statement identifier, in a computer-recognizable manner: l. a conceptual table-of-contents position, and, optionally, a chronological table of contents position, a transactional table of contents 14! position, and a compliance table of contents position, ii. a summary black-letter statement identifier, iii. one or more primary-source item identifiers, iv. one or more topical-index terms. 111. The computerized method of claim 110, wherein said method further comprises: a. writing author comments and author-comment identifiers, and designating them as such in a computer-recognizable manner; and b. assigning the author-comment identifiers to each relevant narrow black-letter statement identifier, in a computer-recognizable manner. 112. The computerized method of claim 110, wherein said method further comprises assigning practice names to relevant narrow black letter statement identifiers, in a computer- recognizable manner. 113. The computerized method of claim 110, wherein said method further comprises writing narrow black-letter statements and narrow black-letter statement identifiers in accordance with drafting rules set forth in the specification herein. 114. A computerized method of authoring and editing computer- readable legal content for use in a computerized research system, wherein said method comprises: a. writing narrow black-letter statement identifiers, and designating them as such in a computer- recognizable manner; and b. assigning to each narrow black-letter statement identifier, in a computer-recognizable manner, one or more primary-source item identifiers. 115. The computerized method of claim 114, wherein said method further comprises writing narrow black-letter statement identifiers in accordance with drafting rules set forth in the specification herein.

Inventors: GOTTSMAN EDWARD J, SANN ALEXANDER, GOTTSMAN, EDWARD, J., SANN, ALEXANDER
Applicants: SANN ALEXANDER, SANN, ALEXANDER
Application year: 2000
Main classification: G06F17
IPC codes: G06F17