This development is illustrated in the statutes of 1223 of the University of Paris, providing that the "booksellers of the University" should produce duplicate copies of the texts authorized for the use of the University, and there is indication that payment was made by the University to scholars for the annotation and proof-reading of such texts. In fact, there existed in France in those days a kind of guild of _libraires jures_ or legalized booksellers, under regulation of the University, as a body of publishers and writers having jurisdiction over the copying and censorship of manuscripts. "Letters of patent" of Charles V, 1368, specified fourteen _libraires_ and eleven _ecrivains_ as registered in Paris, and four chief _libraires_ had jurisdiction over the calling of the _librarius_ and the _stationarius_. The certificate of the correctness of a copy, and perhaps of the right to copy or sell it, may be considered the primitive form of copyright certificate. {Sidenote: Invention of printing} The invention of printing, prior to 1450, made protection of literary property a question of rapidly increasing importance. The new art raised, of course, many new questions wherever the guardians of the law were set to their chronic task of applying old ideas of right to new conditions. The earliest copyright certificate, if it may be so called, in a printed book was that in the reissue of the tractate of Peter Nigrus printed in 1475, at Esslingen, in which the Bishop of Ratisbon certified the correctness of the copy and his approval. At first "privileges" were granted chiefly to printers, for the reproduction of classic or patristic works, but possibly in some cases as the representatives of living writers; and there are early instances of direct grants to authors, the earliest known being in 1486 in Venice to Sabellico. {Sidenote: In Germany} In Germany, the cradle of the art of printing, whence come the earliest _incunabula_ or cradle-books, printing privileges were developed some decades later than in Italy. Koberger, the early Nuremberg printer, whose imprint dates back to 1473, relied rather on the "courtesy of the trade," and indeed made an agreement in 1495 with Kessler of Basel to respect each other's rights. Yet a suit brought in 1480 by Schoeffer, who with Fust had established the first publishing and bookselling business, brought in connection with Fust's heirs against Inkus of Frankfort for the infringement of property rights in certain books, and the issue of a preliminary injunction by a court at Basel, indicated some definite legal _status_.