APA (7th ed.) Citation

Couperus, L. (2010). The Twilight of the Souls. Project Gutenberg.

Chicago Style (17th ed.) Citation

Couperus, Louis. The Twilight of the Souls. Project Gutenberg, 2010.

MLA (9th ed.) Citation

Couperus, Louis. The Twilight of the Souls. Project Gutenberg, 2010.

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