APA (7th ed.) Citation

Simak, C. D. (2009). Empire. Project Gutenberg.

Chicago Style (17th ed.) Citation

Simak, Clifford D. Empire. Project Gutenberg, 2009.

MLA (9th ed.) Citation

Simak, Clifford D. Empire. Project Gutenberg, 2009.

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