In 1964, Pope Paul VI, who had succeeded John XXIII the previous year, established the "Consilium ad exsequendam Constitutionem de Sacra Liturgia", the Council for Implementing the Constitution on the Liturgy. The instruction "Inter oecumenici" of 26 September 1964, issued by the Sacred Congregation of Rites while the Council was still in session, and coming into effect on 7 March 1965 made significant changes to the existing liturgy, though the form of the rite was substantially preserved. Some sources speak of a "1965 Missal", but this generally refers to orders of the Mass that were published with the approval of bishops' conferences, for example, in the United States and Canada, rather than an "editio typica" of the Roman Missal itself. The changes included: use of the vernacular was permitted; free-standing altars were encouraged; there were some textual changes, such as omission of the Psalm "Judica" at the beginning and of the Last Gospel and Leonine Prayers at the end. The 1967 document "Tres abhinc annos", the second instruction on the implementation of the Council's Constitution on the Liturgy, made only minimal changes to the text, but simplified the rubrics and the vestments. Concelebration and Communion under both kinds had meanwhile been permitted, and in 1968 three additional Eucharistic Prayers were authorized for use alongside the traditional Roman Canon.