An appendix is an optional supplement to a research paper where you provide additional and/or more detailed information to give the audience further background reading. Within the body of your paper, you can reference your own appendix or that of another body of work. Either way, follow appropriate American Psychological Association formatting when citing an appendix.
Your Own Appendix
Add your appendix immediately following your reference pages and label it as Appendix A, B, C, etc. Use these labels when discussing the appendix in the body of your paper. In the paper, after the sentence in which you are referencing your appendix, format the in-text citation as (See Appendix A). The letter should match the appropriate appendix label. Do not cite your own appendix on the reference page.
Another Author's Appendix
When using an appendix from another author, include this information on your reference page. For example, a citation on the reference page for an appendix found in a book should read: Author. (year). Appendix A of Title of work. Location: Publisher. The appendix letter should match the appropriate section you are using.