A liturgical book ascribed to Pope Saint Gregory I, called sometimes the Sacramentary of Adrian I, owing to the fact that he sent it to Charlemagne between the years 781,791 when the latter wished to introduce the Roman Rite into his kingdom. The book was copied many times so that there are many versions of it, each containing the additions made by the various scribes. At first these additions were carefully distinguished from the original text, but eventually they became part of it. The book has three parts as follows: