APA (7th ed.) Citation

Doyle, A. C. (2006). The Return of Sherlock Holmes. Project Gutenberg.

Chicago Style (17th ed.) Citation

Doyle, Arthur Conan. The Return of Sherlock Holmes. Project Gutenberg, 2006.

MLA (9th ed.) Citation

Doyle, Arthur Conan. The Return of Sherlock Holmes. Project Gutenberg, 2006.

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