I & A periodicals attempt to cover current literature with as little time lag as possible. Because of time and effort involved in production, speed of reporting literature is not a foremost consideration as in the case of current awareness type publications.
I & A periodicals may be exhaustive or selective in coverage of literature depending upon the purpose. Indexing periodicals, because of comparative ease in production, may aim at an exhaustive coverage of literature. Abstracting periodicals have to be necessarily selective in coverage, as all documents may not be proper for abstracting from the point of view of their content. Hence, abstracting periodicals may, in few cases, include documents with bibliographical description giving indicative abstract only.
I & A periodicals may cover all kinds of primary documents such as books, journal articles, pamphlets and reports, bulletins, patents and standard specifications. In some cases, the cover-age may be limited to a particular kind of documents. There are also I&A periodicals devoted to unpublished literature and sources such as research reports, university theses and dissertations, proceedings of conferences, seminars, meetings, etc. are also covered therein.