APA (7th ed.) Citation

Santayana, G. (2009). Some Turns of Thought in Modern Philosophy. Project Gutenberg.

Chicago Style (17th ed.) Citation

Santayana, George. Some Turns of Thought in Modern Philosophy. Project Gutenberg, 2009.

MLA (9th ed.) Citation

Santayana, George. Some Turns of Thought in Modern Philosophy. Project Gutenberg, 2009.

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