"Gautama is the primary figure in Buddhism, and account of his life, discourses, and monastic rules are believed by Buddhists to have been summarized after his death and memorized by his followers. Various collections of teachings attributed to him were passed down by oral tradition, and first committed to writing about 400 years later."
Fowler, Mark. Zen Buddhism: beliefs and practices. Sussex Academic Press. 2005. p. 32
