APA (7th ed.) Citation

Smith, W. (2011). The History of the Post Office in British North America. Project Gutenberg.

Chicago Style (17th ed.) Citation

Smith, William. The History of the Post Office in British North America. Project Gutenberg, 2011.

MLA (9th ed.) Citation

Smith, William. The History of the Post Office in British North America. Project Gutenberg, 2011.

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