By the year 1495, the book-trade of Leipsic had assumed very considerable proportions and was already beginning to rival that of Frankfort. The Booksellers’ Association, organised (in Frankfort) in 1525, is at the present time, four centuries later, the most effective and intelligently managed trade organisation that the world has known. Leipsic publishers gave from an early period special attention to the printing of the controversial literature of the Reformation, and, as was natural from their close relations with Wittenberg, the sympathies of the larger proportion of the printers were in accord with the Lutherans. In 1524, Duke George, who was a Catholic, came to the throne and during his reign, which continued until 1533, the writings of the reformers were repressed by a rigorous censorship. The Duke utilised the machinery of the trade organisation for putting into effect the ducal regulations for supervision and censorship, and two ecclesiastical censors, appointed under the ducal authority, secured the aid of the city officials in making examination of all the books printed and in confiscating or cancelling all heretical works found in the shops of either Leipsic or Dresden. The immediate result of these anti-reform operations of the Church and of the Duke was the practical destruction for the time being of the book-trade of Leipsic. Many of the printers transferred their presses to Wittenberg or Magdeburg. In 1526, occurred in Leipsic an extreme instance of the application of Catholic censorship. Under the instructions of Duke George, Johann Herrgott, a printer and colporteur, was burned, with certain of his books, for the crime of distributing Protestant literature. In the next year, Hübmayer, the leader of the Baptists in Southern Germany, was burned in Vienna for a similar offence. In 1571, the Duke of Saxony ordered that the work of the printers should be restricted to three towns, Leipsic, Dresden, and Wittenberg. The purpose of this regulation was the facilitating of censorship control. [Sidenote: Wittenberg] In advance of the aggressive Protestant measures of Luther, Wittenberg had already become an important place for book-production, having secured, among other favourable influences, the advantage of the transfer of certain of the printers and their presses from Leipsic. After 1515, Wittenberg was the most important of the centres from which were distributed throughout Germany the books and pamphlets (_Flugschriften_) of the reformers. It was in Wittenberg also that was brought into print the great Bible of Luther. [Sidenote: Magdeburg]