The production of books and manuscripts in the fifteenth century saw the culmination of tendencies which had begun during the latter part of the thirteenth century. It is important to distinguish between 'mere books' and illuminated manuscripts, produced on the finest sheepskin or goatskin parchment. The use of paper in book production was evident from the late fourteenth century onwards. Parchment provided a better medium for manuscript painters, and was far better suited to the production of de luxe editions for affluent patrons and clients. The fifteenth century also saw an unprecedented demand for illustrated books at social levels. The manufacture and sale of books was only loosely controlled by guilds and corporations. The tendency towards the establishment of publishing houses, was especially marked in the Low Countries and at Florence. The important development in the style and format of illuminated books stemmed from the emergence of a closer relationship between manuscript painting and the art of the panel painter.