APA (7th ed.) Citation

Schiller, F. (1990). The history of the Thirty Years' War. Project Gutenberg.

Chicago Style (17th ed.) Citation

Schiller, Friedrich. The History of the Thirty Years' War. Champaign, Ill: Project Gutenberg, 1990.

MLA (9th ed.) Citation

Schiller, Friedrich. The History of the Thirty Years' War. Project Gutenberg, 1990.