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
The Owl (Purdue Online Writing Lab)
Page last updated on October 7, 2022