However, its attribution to Pope Gregory I (590-604) shows us that Gregory did much to reform the liturgy. A constant tradition ascribes such a work to him, as to Gelasius. John the Deacon (eighth century) in his "Life of Gregory" expresses this tradition: "He collected the Sacramentary of Gelasius in one book, leaving out much, changing little, adding something." Pope Adrian himself, in sending the book to Charlemagne, said that it was composed "by our holy predecessor, the divinely speaking Pope Gregory". The fact that the essential foundation of this sacramentary goes back to St Gregory, indeed to long before his time, is certain. We do not doubt that he made such changes as those that are acclaimed to him by his biographer, and that these changes stand in this book. But his work has not remained untouched, additions have been made to it since his time. For example, the addition of his own feast as well as other feasts that had not been celebrated before the seventh century. The book sent by Pope Adrian to Charlemagne has gone through inevitable development over the centuries since Gregory finished it. It represents the Roman Rite of the time when it was sent - the eighth century. In the Frankish kingdom, copies were made for churches and additions of other Masses and prayers were added according to the specific church's requests. These additions were taken partly from the Gelasian book, partly from Gallican sources. Though at first the additions were carefully distinguished from the original book, they were eventually incorporated in it. Between the ninth and eleventh centuries the book, including the additions, returned to Rome, took the place of the original pure Roman Rite, and so became the foundation of the Roman Missal.