and devoted Immaculist, placed it on the Roman calendar (i.e., list of church festivals and observances) via the bull Cum praexcelsa. Thereafter in 1481 and 1483, in response to the polemic writings of the prominent Thomist, Vincenzo Bandello, Pope Sixtus IV published two more bulls which forbade anybody to preach or teach against the Immaculate Conception, or for either side to accuse the other of heresy, on pains of excommunication.