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Catholic Church. Pope (1978-2005 : John Paul II) agus Pope John Paul II. Encyclical Letter Sollicitudo Rei Socialis of the Supreme Pontiff, John Paul II, to the Bishops, Priests, Religious Families, Sons and Daughters of the Church and All People of Good Will for the Twentieth Anniversary of Populorum Progressio. Washington, D.C.: Office of Publishing and Promotion Services, United States Catholic Conference, 1988.

Catholic Church. Pope (1978-2005 : John Paul II) agus Pope John Paul II. Encyclical Letter Sollicitudo Rei Socialis of the Supreme Pontiff, John Paul II, to the Bishops, Priests, Religious Families, Sons and Daughters of the Church and All People of Good Will for the Twentieth Anniversary of Populorum Progressio. Office of Publishing and Promotion Services, United States Catholic Conference, 1988.