Quadragesimo anno (Latin) is literally "in the fortieth year", being the first words of the 1931 encyclical of Pope Pius XI (1857-1939; Pope, 1922-1939). This encyclical refers to and amplifies the Rerum Novarum (on new things) encyclical promulgated by Pope Leo XIII (1810-1903; Pope, 1878-1903) forty years earlier (1891). Taken together, these two encyclicals present the official position of the Roman Catholic Church on the social order, including socialism and capitalism.
- Percy L. Greaves, Jr. "Mises Made Easier ", 1974. Referenced 2014-08-21.