The manuscripts were begun in Milan while Leonardo was under the service of Ludovico Sforza (between 1482 and 1499), being worked on substantially for the last 25 years of Leonardo's life. The works later published in this collection drew from the writing of Leon Battista Alberti and Cennino Cennini. Upon Leonardo's death, he left his notebooks to his pupil and heir Francesco Melzi to be published, a task of overwhelming difficulty because of its scope and Leonardo's idiosyncratic writing. Sometime before 1542, Melzi gathered together the papers for A Treatise on Painting from 18 of Leonardo's 'books' (two-thirds of which have gone missing). After Melzi's death in 1570, the collection passed to his son, the lawyer Orazio, who initially took little interest in the journals, but they were later dispersed. A version of the treatise was published in France in 1632.[12] It was printed in an abridged form in French and Italian as Trattato della pittura by Raffae