APA (7th ed.) Citation

Ingersoll, R. G. (2011). The Christian Religion An Enquiry. Project Gutenberg.

Chicago Style (17th ed.) Citation

Ingersoll, Robert Green. The Christian Religion An Enquiry. Project Gutenberg, 2011.

MLA (9th ed.) Citation

Ingersoll, Robert Green. The Christian Religion An Enquiry. Project Gutenberg, 2011.

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