APA (7th ed.) Citation

Roget, P. M. (1991). Roget's Thesaurus. Project Gutenberg.

Chicago Style (17th ed.) Citation

Roget, Peter Mark. Roget's Thesaurus. Project Gutenberg, 1991.

MLA (9th ed.) Citation

Roget, Peter Mark. Roget's Thesaurus. Project Gutenberg, 1991.

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