Pius X, P. (1904). The XIII Centenary of St. Gregory, Encyclical Letter of Pius X. New York.
Chicago Style (17th ed.) CitationPius X, Pope. The XIII Centenary of St. Gregory, Encyclical Letter of Pius X. New York, 1904.
MLA (8th ed.) CitationPius X, Pope. The XIII Centenary of St. Gregory, Encyclical Letter of Pius X. New York, 1904.
Warning: These citations may not always be 100% accurate.