APA
Pius XI, . (1930). Encyclical letters of Pope Pius XI on christian marriage. St. Paul: St. Paul Editions.
Chicago
Pius XI, . 1930. Encyclical letters of Pope Pius XI on christian marriage. St. Paul: St. Paul Editions.
Harvard
Pius XI, . (1930). Encyclical letters of Pope Pius XI on christian marriage. St. Paul: St. Paul Editions.
MLA
Pius XI, . Encyclical letters of Pope Pius XI on christian marriage. St. Paul: St. Paul Editions. 1930.
