Some indexes cover a broad range of subjects while other indexes are devoted to a single discipline. Indexes that provide summaries of the articles listed in them are called abstracts. Examples of indexes with abstracts are Chemical Abstracts and Psychological Abstracts . Print volumes provide references to the literature published during a particular period, often in monthly and annual volumes.
Database indexes cover the literature spanning several years or more.
It is important to know if the index timespan is adequate for any particular search. The Library's catalogue. In most cases, the information you find in an index in book format will be identical to the information you find in the corresponding database. Databases may compile references from a number indexing sources. Also, certain databases provide the full text of some of the articles referenced.