The present contribution interprets the results of the statistic of explicit sources employed in the first volume of Pelbartus of Themeswar’s Rosarium. This author was a late 15th century Hungarian Observant Franciscan who wrote a number of texts that were real “bestsellers” in his time and in the century following his death. The Rosarium is his work of theoretic theology and the one closest to what might be called a medieval philosophical endeavor. By seeing who he quotes and in what way, we get to showcase his doctrinal preference for the Scotist school and, as a bonus, identify some of the works that the 15th century library of the “Saint John” Observant convent of Buda, where he worked during the last period of his life, owned.