Pius XI, P. (1930). Why a retreat? "Mens nostra," the encyclical of Pope Pius XI on Laymen's retreats. New York.
Chicago Style (17th ed.) CitationPius XI, Pope. Why a Retreat? "Mens Nostra," the Encyclical of Pope Pius XI on Laymen's Retreats. New York, 1930.
MLA (8th ed.) CitationPius XI, Pope. Why a Retreat? "Mens Nostra," the Encyclical of Pope Pius XI on Laymen's Retreats. New York, 1930.
Warning: These citations may not always be 100% accurate.