APA (7th ed.) Citation

Thorndike, E. L. (2012). The Psychology of Arithmetic. Project Gutenberg.

Chicago Style (17th ed.) Citation

Thorndike, Edward L. The Psychology of Arithmetic. Project Gutenberg, 2012.

MLA (9th ed.) Citation

Thorndike, Edward L. The Psychology of Arithmetic. Project Gutenberg, 2012.

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