Encyclicals of Pope John XXIII Ad Petri CathedramTruth, Unity and PeaceJune 29, 1959 Aeterna Dei SapientiaCommemorating the Fifteenth Centennial of the Death of Pope St. Leo I: The See of Peter as the Center of Christian UnityNovember 11, 1961 Grata Recordatioon the Rosary: Prayer for the Church, Missions, International and Social ProblemsSeptember 26, 1959 Mater et MagistraChristianity and Social ProgressMay 15, 1961 Pacem In Terrison the Establishing Universal Peace in Truth, Justice, Charity, and LibertyApril 11, 1963 Paenitentiam Agereon the Need for the Practice of Interior and Exterior PenanceJuly 1, 1962 Princeps Pastorumon the Missions, Native Clergy, and Lay ParticipationNovember 28, 1959 Sacerdotii Nostri Primordiaon St. John VianneyAugust 1, 1959