APA
Leo XIII P. X., . (1931). Three Great Encyclicals : Labor ; Education ; Marrige. New York: Paulist Press.
Chicago
Leo XIII Pius XI, . 1931. Three Great Encyclicals : Labor ; Education ; Marrige. New York: Paulist Press.
Harvard
Leo XIII P. X., . (1931). Three Great Encyclicals : Labor ; Education ; Marrige. New York: Paulist Press.
MLA
Leo XIII Pius XI, . Three Great Encyclicals : Labor ; Education ; Marrige. New York: Paulist Press. 1931.
