There is really only one true guide to the APA style, and that is the APA Publication Manual. The quality of APA style guides on the Internet vary, and only provide a small sample of what the book contains.
Publication Manual of the American Psychological Association: The Official Guide to APA Style (7th edition)
BF76.7 .P83 2020
Purdue Owl Writing Lab: APA Style
A quick guide to APA formats
Page last updated on January 3, 2023