APA (7th ed.) Citation

Libby, W. (2012). An Introduction to the History of Science. Project Gutenberg.

Chicago Style (17th ed.) Citation

Libby, Walter. An Introduction to the History of Science. Project Gutenberg, 2012.

MLA (9th ed.) Citation

Libby, Walter. An Introduction to the History of Science. Project Gutenberg, 2012.

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