Papal letters to the Universal Church or, in many cases, especially before Vatican II, to the Bishops in communion with the Holy See. Worthy of special attention besides Rerum Novarum (see previous post) are Quadragesimo Anno, Mater et Magistra, Pacem in Terris, Populorum Progressio, Laborum Exercens, Sollicitudo Rei Socialis, Centesimus Annus, Caritas in Veritate, Fides et Ratio, and Spe Salvi. As of this post, the Vatican has online the encyclicals of Leo XIII, Pius X, Benedict XV, Pius XI, Pius XII, John XXIII, Paul VI, John Paul II, Benedict XVI, and Francis. ISBN recommendation: 0-87650-259-1
A joint Catholic-Orthodox declaration, proclaimed 7 December 1965, committing the excommunications, related to Papal embassy to Constantinople in 1054, to oblivion. Image links to Vatican translation.
Decrees of the Second Vatican Council (A.D. 1962-65), summoned by Pope John XXIII. A Council of renewal by which the Church is called to reach out to the Modern world in solidarity – presenting Christ as the relevant Truth even in the present age. Image above links to Vatican translations. ISBN recommendation: 0-87840-490-2
Decrees of the First Vatican Council (A.D. 1869-70), summoned by Pope Pius IX. The Council condemned as erroneous philosophical naturalism, pantheism, materialism, and atheism. It also confirmed each successor to the chair of Peter to be, as Vicar of Christ, sovereign head of the Church militant. Image above links to Tanner translation. ISBN recommendation: 0-87840-490-2