The history of the development of canon law in England becomes much more complicated when we pass from the eleventh to the twelfth century. It is not that material is lacking, but that the material is so various and cannot be arranged in its proper chronological order. We can only say what the surviving manuscripts show to have been in England in the twelfth century; we cannot say when it came here. We may draw a line between the pre-Gratian collections and Gratian, but that line will not mark a clear-cut division of time. Some of the older collections probably continued to enter the country, and certainly were still being copied, after the arrival of Gratian; it doubtless took a little time for students to discriminate and to recognise that Gratian made the others unnecessary. Ivo's Pannortnia, at any rate, was so popular that it was still being copied in the thirteenth century. We have to discriminate, too, between the collections which were in general circulation and those which only attained to a limited circulation. Lanfranc's collection, as we have seen, is in the first category; and with it must be included both Ivo and Gratian. It is only these two authors that, for the same period, hold this position on the Continent also. The other collections, in England as elsewhere, are confined to a few libraries only.