Publication Manual of the American Psychological Association by Some online guides for APA style:
APA QUICK GUIDE - From APA, includes clearly-laid out citations the 3 most-used source types
Current APA Guide--From Tomlinson Library, updated for the 7th edition
Purdue Online Writing Lab Guide—Detailed overview of all aspects of writing and citing in APA style
The Good Writing Guide for Education Students by 
Doing Academic Writing in Education
Publish,Flourish,and Make a Difference
Oxford Paperback Thesaurus
Oxford Dictionary of Quotations
The Oxford Dictionary of American Usage and Style