 He had performed important services for the diffusion of classical authors when Nicholas V, the true founder of the Vatican Library, became pope.He devoted fourteen years to collecting the library of Federico da Montefeltro, the Duke of Urbino, organizing it in a more modern manner; it contained the catalogues of the Vatican, of San Marco, Florence, of the Visconti Library at Pavia, and Oxford.Vespasiano had a limited knowledge of Latin, and he is one of the few writers of the time who acknowledged it.