Catholic Church. Pope (1958-1963 : John XXIII) & John XXIII, P. (1961). Encyclical letter on Pope Leo the Great. National Catholic Welfare Conference.
Chicago Style (17th ed.) CitationCatholic Church. Pope (1958-1963 : John XXIII) and Pope John XXIII. Encyclical Letter on Pope Leo the Great. [Washington, D.C.: National Catholic Welfare Conference, 1961.
MLA (8th ed.) CitationCatholic Church. Pope (1958-1963 : John XXIII) and Pope John XXIII. Encyclical Letter on Pope Leo the Great. National Catholic Welfare Conference, 1961.
Warning: These citations may not always be 100% accurate.