 One method to obtain information on the oldest core of Buddhism is to compare the oldest extant versions of the Theravadin Pāli Canon, the surviving portions of the scriptures of Sarvastivada, Mulasarvastivada, Mahīśāsaka, Dharmaguptaka and other schools, and the Chinese āgamas and other surviving portions of other early canons (such as the Gandharan texts).Early proto-Mahayana texts which contain nearly identical material to that of the Pali Canon such as the Salistamba Sutra are also further evidence.The beginning of this comparative study began in the 19th century, Samuel Beal published comparative translations of the Pali patimokkha and the Chinese Dharmaguptaka pratimoksa (1859), showing they were virtually identical.