APA (7th ed.) Citation

Vaughan, J. S. (2005). The Purpose of the Papacy. Project Gutenberg.

Chicago Style (17th ed.) Citation

Vaughan, John S. The Purpose of the Papacy. Project Gutenberg, 2005.

MLA (9th ed.) Citation

Vaughan, John S. The Purpose of the Papacy. Project Gutenberg, 2005.

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