APA (7th ed.) Citation

Doyle, A. C. (2005). The Adventure of the Red Circle. Project Gutenberg.

Chicago Style (17th ed.) Citation

Doyle, Arthur Conan. The Adventure of the Red Circle. Project Gutenberg, 2005.

MLA (9th ed.) Citation

Doyle, Arthur Conan. The Adventure of the Red Circle. Project Gutenberg, 2005.

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