For APA style, you should cite the work using the author's last name and the date of publication in parentheses. For example: (Jones, 2003). If there are multiple authors (but no more than five), cite the resource by listing all of the authors in the first reference and listing the first author's last name and "et al." in subsequent references. For example: (Harris, Jones & Smith, 2003) and (Harris et al., 2003). If any authors have the same last name, include first name initials to distinguish between each author. Finally, if there are more than six authors, cite by simply using the first author, et al. and the date. For example: (Harris et al., 2003).
Some resources won't have an author available. Cite a work that doesn't have an author by putting the title and the date in parentheses. Book titles should be italicized while other titles are in quotation marks. If the title of the resource is long, you can just use the first couple of words of the title. For example: ("Exploring Narnia," 1998). If the work lists the author as anonymous, put that in the citation. For example: (Anonymous, 2007).
Personal communications can include letters, interviews or emails. You should cite personal communication by listing the person's name, the date and the notation that it was a personal communication. For example: (M. Hamilton, personal communication, May 23, 2008). It is important to note that it is a personal communication since you won't cite these resources on the reference list. The in-text citation is the only citation for these sources and should be accurately noted.
An electronic source, such as an article, webpage or an entry from a database should be cited the same as a source by any other reference with an author. If you don't know the author, use the title as previously discussed. If you don't know the date of publication, a common issue with electronic sources, put "n.d." in the parentheses. For example: (Smith, n.d.) or ("Exploring Narnia," n.d.).