In-text citations tell readers that additional information about the outside sources you have used in your research can be found on the reference page at the end of your paper. Remember that each in-text citation in the body of your paper must be listed on your reference
page and vice versa. The APA Manual lists two exceptions to this rule: (1) classical works that are standardized (e.g., religious and ancient texts); and (2) personal communication that cannot be readily retrieved (e.g., private emails, letters, and memos).
 
Here is a list of common source types, with each linked to a page containing format instructions and best practices. 

All formatting guides pertain to both print and electronic sources.


Formats for Quotation, Paraphrase, and Summary

Works by Multiple Authors
                                                  
Works by Unknown Authors

Works with No Date

Groups as Authors

Direct Quotes of 40 Words or More 
                                                 
  Secondary Sources
                                                        
Personal Communications
                                                  

For more information on source types and in-text citations, consult Publication Manual of the American Psychological Association, 7e.