APA (7th ed.) Citation

Doyle, A. C. (2005). The Adventure of the Cardboard Box. Project Gutenberg.

Chicago Style (17th ed.) Citation

Doyle, Arthur Conan. The Adventure of the Cardboard Box. Project Gutenberg, 2005.

MLA (9th ed.) Citation

Doyle, Arthur Conan. The Adventure of the Cardboard Box. Project Gutenberg, 2005.

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