Athanasius knew Greek and admitted not knowing Hebrew [see, e.g., the 39th Festal Letter of St. Athan.]. The Old Testament passages he quotes frequently come from the Septuagint Greek translation. Only rarely did he use other Greek versions (to Aquila once in the Ecthesis, to other versions once or twice on the Psalms), and his knowledge of the Old Testament was limited to the Septuagint. Nonetheless, during his later exile, with no access to a copy of the Scriptures, Athanasius could quote from memory every verse in the Old Testament with a supposed reference to the Trinity without missing any.[citation needed] The combination of Scriptural study and of Greek learning was characteristic of the famous Alexandrian School.