transfer from individual to corporate leadership. None of the Society's publications after 1942 acknowledged authorship, and were instead attributed to an anonymous Writing Committee. From about 1944, the term "governing body" began to be used with a measure of frequency, with the term initially applied to the Watch Tower Society's seven-man Board of Directors. Knorr began a campaign of real estate acquisition in Brooklyn to expand the organisation's world headquarters, expanded printing production throughout the world, and organized a series of international assemblies that dwarfed those of Rutherford in the 1920s. In 1958, more than 253,000 Witnesses gathered at two New York City venues, Yankee Stadium and the Polo Grounds, for an eight-day convention where more than 7,000 were baptized. Other large conventions were held in the US, Canada and Germany. He instituted major training programs, including the Watchtower Bible School of Gilead to train missionaries, and the Theocratic Ministry School to give instruction in preaching and public speaking at the congregational level. He commissioned a new translation of the Bible, which was released progressively from 1950. It was published as the complete New World Translation of the Holy Scriptures in 1961. Also produced were a Greek-English New Testament interlinear, The Kingdom Interlinear Translation of the Greek Scriptures, and a Bible encyclopedia, Aid to Bible Understanding. The offices of elder and ministerial servant (deacon) were restored to Witness congregations in 1972, with appointments being made from headquarters. Knorr's vice-president, Frederick William Franz, became the leading theologian for the group and the pace of doctrinal change slowed. Blood transfusions were prohibited for Witnesses from 1945. In 1961 the eating of blood in meat was prohibited. The Watchtower instructed Witnesses to check with their butcher whether the animals and fowl he sold had been properly drained of their blood. Birthday celebrations were described as "objectionable" in 1951 because of their pagan origins, and other explicit rules regarding acceptable conduct among members were introduced, with a greater emphasis placed on disfellowshipping as a disciplinary measure. Adult male Witnesses in the US, Britain, and some European countries were jailed for refusal of military service in the post-war years, with particularly harsh treatment meted out in Portugal, Spain, Italy, Greece, East Germany and Romania. Wide-scale persecution of Witnesses in several African nations was launched between 1967 and 1975, with as many as 21,000 fleeing Malawi to refugee camps in Zambia after a series of murders