APA (7th ed.) Citation

Riga, P. (1964). Peace on earth: A community on Pope John's encyclical. Herder and Herder.

Chicago Style (17th ed.) Citation

Riga, Peter. Peace on Earth: A Community on Pope John's Encyclical. [New York]: Herder and Herder, 1964.

MLA (9th ed.) Citation

Riga, Peter. Peace on Earth: A Community on Pope John's Encyclical. Herder and Herder, 1964.