APA (7th ed.) Citation

Stevenson, R. L. (2001). Letters of Robert Louis Stevenson. Project Gutenberg.

Chicago Style (17th ed.) Citation

Stevenson, Robert Louis. Letters of Robert Louis Stevenson. Champaign, IL: Project Gutenberg, 2001.

MLA (9th ed.) Citation

Stevenson, Robert Louis. Letters of Robert Louis Stevenson. Project Gutenberg, 2001.