APA (7th ed.) Citation

Gill, J. (1961). Eugenius IV: Pope of Christian union. The popes through history.

Chicago Style (17th ed.) Citation

Gill, Joseph. "Eugenius IV: Pope of Christian Union." The Popes Through History 1961.

MLA (8th ed.) Citation

Gill, Joseph. "Eugenius IV: Pope of Christian Union." The Popes Through History, 1961.

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