Putnam, William Lowell (2006). "Appendex B". The Mountaineer's Pontiff: Achille Ratti. Light Technology Publishing. ISBN9781622336906.[page needed] According to Putnam, Pius named 75 cardinals, not 76, possibly counting Billot's resignation as a subtraction.
Murphy, Joseph J. (October 1914). "Pius X and the Cardinalate". The Ecclesiastical Review. LI. Philadelphia: The Dolphin Press: 440ff. Retrieved 6 March 2021.
José M. Sánchez (April 1963). "The Second Spanish Republic and the Holy See: 1931-1936". Catholic Historical Review. 49 (1): 47–68, esp. 65–6. JSTOR25017192.