The condition of the working classes. (Encyclical letter, May 15, 1891).--On the evils affecting modern society, their causes and remedies. (Encyclical letter, April 21,1878).--The Christian constitution of states. (Encyclical letter, November 1, 1885).--On the chief duties of Christians as citizens. (Encyclical letter, January 10, 1890).--Human liberty. (Encyclical letter, June 20, 1888).--Christian marriage. (Encyclical letter, February 10, 1880).--The right ordering of Christian life. (Encyclical letter, December 30, 1888).--Concerning modern errors, socialism, communism, nihilism. (Encyclical letter, December 28, 1878).--Working men's clubs and associations. (An address to the officials and members of the societies for the furtherance of Catholic interests amongst the industrial classe in France, February 24, 1885).--The reunion of Christendom. (Encyclical letter, June 20, 1894)