"Caesar writes in De Bello Gallico VI, 13: “[The Druids] are concerned with divine worship… sacrifices… ritual… Numerous young men gather round them for the sake of instruction holding them in great honour”; in ch VI, 14 he adds, “In the schools of the Druids they learn by heart a great number of verses, and therefore some persons remain twenty years under training. And they do not think it proper to commit these utterances to writing, although in almost all other matters… they make use of Greek letters”."