APA (7th ed.) Citation

Sumner, W. G. (2006). What Social Classes Owe to Each Other. Project Gutenberg.

Chicago Style (17th ed.) Citation

Sumner, William Graham. What Social Classes Owe to Each Other. Project Gutenberg, 2006.

MLA (9th ed.) Citation

Sumner, William Graham. What Social Classes Owe to Each Other. Project Gutenberg, 2006.

Warning: These citations may not always be 100% accurate.