APA (7th ed.) Citation

Paul VI, P. (1968). On the regulation of birth = Humanae vitae: Encyclical letter. Washington, D.C..

Chicago Style (17th ed.) Citation

Paul VI, Pope. On the Regulation of Birth = Humanae Vitae: Encyclical Letter. Washington, D.C., 1968.

MLA (8th ed.) Citation

Paul VI, Pope. On the Regulation of Birth = Humanae Vitae: Encyclical Letter. Washington, D.C., 1968.

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