APA (7th ed.) Citation

Seignobos, C., Langlois, C. V., & Berry, G. G. (2009). Introduction to the Study of History. Project Gutenberg.

Chicago Style (17th ed.) Citation

Seignobos, Charles, Charles Victor Langlois, and George Godfrey Berry. Introduction to the Study of History. Project Gutenberg, 2009.

MLA (9th ed.) Citation

Seignobos, Charles, et al. Introduction to the Study of History. Project Gutenberg, 2009.

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