APA (7th ed.) Citation

Mark Twain. (2010). Roughing it. Project Gutenberg.

Chicago Style (17th ed.) Citation

Mark Twain. Roughing It. To be supplied: Project Gutenberg, 2010.

MLA (8th ed.) Citation

Mark Twain. Roughing It. Project Gutenberg, 2010.

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