APA (7th ed.) Citation

Leith, C. K. (2009). The Economic Aspect of Geology. Project Gutenberg.

Chicago Style (17th ed.) Citation

Leith, C. K. The Economic Aspect of Geology. Project Gutenberg, 2009.

MLA (9th ed.) Citation

Leith, C. K. The Economic Aspect of Geology. Project Gutenberg, 2009.

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