Bird, B. Rebel before his time, 1987 t.p. (John Ball) p. i (leader of the Peasants' Revolt 1381) p. 16 (John Ball had attained the age of 21 in 1352; this would give his birth date as some time in 1331)
DNB (Ball, John, d. 1381, priest, fomented insurrection of Wat Tyler)