Some works are current, some are retrospective, and it saves time to know which is which. Maps often have a larger scale and include more detail than atlas maps do. Historical atlases assist in the study of boundary changes, military campaigns, and early exploration. See Books in Print . Subject bibliographies list works on a specified subject.
Periodical bibliographies list the titles of periodicals, magazines, and journals.
Union catalogs list and describe the collections of more than one library. Indexes and Abstracts provide greater detail about a source. For instance, a poetry index might list the titles of the poems in several major collections of poetry, a periodical index might list the articles within one or more periodicals, etc. Click here for a list of the major periodical indexes and abstracts available online or at the BBC Library. Libraries Unlimited, Inc., 1995.