w2

https://owl.purdue.edu/owl/general_writing/the_writing_process/developing_an_outline/index.html

https://owl.purdue.edu/owl/general_writing/the_writing_process/developing_an_outline/types_of_outlines.html

https://owl.purdue.edu/owl/general_writing/the_writing_process/developing_an_outline/how_to_outline.html

https://ebookcentral.proquest.com/lib/apus/detail.action?docID=3407594