APA style calls for a list of references instead of a bibliography. The requirements of a reference list are that all references cited in the text of a paper must be listed alphabetically by first author's last name in the list of references and that all references listed must be cited within the text. A bibliography, on the other hand, typically includes resources in addition to those cited in the text and may include annotated descriptions of the items listed. In general, the list of references is double-spaced and listed alphabetically by first author's last name. For each reference, the first line is typed flush with the left margin, and any additional lines are indented as a group a few spaces to the right of the left margin (this is called a hanging indent).