 Or the letters were called sententiæ, i. e. opinions; præcepta; auctoritates.On the other hand, more general letters, especially those of dogmatic importance, were also called at times "tomi; indiculi; commonitoria; epistolae tractoriae", or simply "tractatoriae".If the matter were important, the popes issued the letters not by their sole authority, but with the advice of the Roman presbytery or of a synod.