In Nuremberg, under a regulation of 1513, the printers were to be sworn each year as holding the orthodox Catholic faith and as agreeing to print no books contrary to that faith.[146] The magistrates issued in 1518 a special prohibition against the printing of the writings of the Hussites, and in 1521, a similar prohibition against the writings of Luther, Calvin, and Zwingli. This edict was withdrawn in 1535 when the magistracy of the city had become Lutheran. In 1527, the poet-cobbler, Hans Sachs, came under censorship for certain rhymes attached to an illustrated record of the Tower of Babel. In this case, the trouble appears, however, to have been not religious, but a matter of guild prejudice. Sachs, being licensed only as a cobbler, had no authority to do work as a poet. After 1535, when the control of Nuremberg had passed into the hands of the Protestants, there is a rapid development of the activity of its printing-presses and book-trade. [Sidenote: Tübingen Breslau] The works of Melanchthon were first printed in Tübingen in 1511. Later, Melanchthon used for his theological treatises and also for his long series of text-books the presses of Wittenberg. The statutes of the University of Tübingen in regard to the _Libelli famosi_ were, in 1500, made binding throughout the electorate of Würtemberg. In 1557, an edict of the Duke called for an annual visitation of the bookshops for the search for heretical publications. In 1593, a ducal permission was given to one bookseller in Tübingen, Gruppenbach, to buy for the use of the professors two copies of any heretical books called for. In 1601, an ordinance was published in Tübingen prohibiting the sale of all sectarian or controversial books, Catholic as well as Protestant. In the three ecclesiastical principalities of Mayence, Cologne, and Trier, the ecclesiastical censorship became, after 1525, particularly rigorous with the result of a material checking in the business of the printers and booksellers. In Silesia, Breslau became the centre of Catholic influence and the Protestant printers were, after 1577, largely driven out of business. [Sidenote: Heidelberg] In Heidelberg, under an edict of the Elector of Baden, the censorship control was, in 1651, placed in the hands of the university and came under the direction of the theological faculty. [Sidenote: Vienna]