APA (7th ed.) Citation

Leo XIII, P. C. C. P. (1942). Diuturnum, On Civil Government, Encyclical Letter of Pope Leo XIII. New York.

Chicago Style (17th ed.) Citation

Leo XIII, Pope; Catholic Church. Pope. Diuturnum, On Civil Government, Encyclical Letter of Pope Leo XIII. New York, 1942.

MLA (8th ed.) Citation

Leo XIII, Pope; Catholic Church. Pope. Diuturnum, On Civil Government, Encyclical Letter of Pope Leo XIII. New York, 1942.

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