APA (7th ed.) Citation

Rusch, W. G. (2011). Gregory I. Encyclopedia of Christianity online. doi:10.1163/2211-2685_eco_G266

Chicago Style (17th ed.) Citation

Rusch, William G. "Gregory I." Encyclopedia of Christianity Online 2011, https://doi.org/10.1163/2211-2685_eco_G266.

MLA (8th ed.) Citation

Rusch, William G. "Gregory I." Encyclopedia of Christianity Online, 2011, https://doi.org/10.1163/2211-2685_eco_G266.