Summi Pontificatus : [Encycliek 20 oct. 1939].

MLA

Pius. Summi Pontificatus : [encycliek 20 Oct. 1939]. Fribourg: Ed. St-Paul, 1958.

APA

Pius, P. (1958). Summi Pontificatus : [Encycliek 20 oct. 1939]. Fribourg: Ed. St-Paul.

Chicago

Pius Summi Pontificatus : [encycliek 20 Oct. 1939]. Fribourg: Ed. St-Paul, 1958.