A bibliography is a list, either indicative or comprehensive, of writings used or considered by an author in preparing a particular work.Formats vary, but an entry for a book in a bibliography usually contains the following information about it:author(s)titlepublisherdate of publicationAn entry for a journal or periodical article usually contains:author(s)article titlejournal titlevolumepagesdate of publicationA bibliography may be arranged by author, topic, or some other scheme.Annotated bibliographies give descriptions about how each source is useful to an author in constructing a paper or argument. These descriptions, usually a few sentences long, provide a summary of the source and describe its relevance. Bibliographies differ from library catalogs by including all relevant items rather than all items that are actually in a particular library. However, some national libraries’ catalogs also serve as national bibliographies, as they contain almost all their countries’ publications.