Source citations lend an expertise and transparency to any published work. Whereas bibliographies simply organize sources for the ease of research verification, an annotated bibliography explains not only the qualifications of the source, but why it was used as support material. Cornell University Library states, "The purpose of the annotation is to inform the reader of the relevance, accuracy, and quality of the sources cited." Annotated bibliographies explain the author's point of view and help the reader better understand his or her argument.
Simple and annotated bibliographies typically contain the most relevant information about a source: author, title, and time and place of publication. This information will naturally vary, depending on the source type (book, scholarly article of CD, for example). Additionally, sources within bibliographies can be organized by theme, especially if the bibliography is long. According to the Yale Library, bibliographies can be listed by time period, nationality, timeliness and frequency of the cited sources. These bibliographic types are called "Current," "National," "Period," "Retrospective," "Serial" and "Subject."
According to APA, the "APA style was developed by social and behavioral scientists to standardize scientific writing." Citations in this format will generally list information in the following order: author or editor name(s), date of publication, title and publication data. Citations will be double-spaced and use a hanging indent paragraph style. Annotations will be indented an additional two spaces from the citation and are usually around 150 words in length.
The other two main types of standardized writing and citation styles come from the Modern Language Association (MLA) and the Chicago Manual of Style (CMS). MLA style is favored by non-scientific disciplines, such as English and other liberal arts studies. CMS is used frequently in scholarly historical research and by book publishers. Though there are subtle differences among citation types, MLA and CMS differ from APA by placing the date of publication at the end of the citation.