The importance to scholars of the papal registers and other records in the Vatican Archives as a source for later medieval history scarcely needs to be emphasised. From the thirteenth century onwards, the different series of records proliferated. They begin with registers of outgoing correspondence, known as the Vatican Registers, in the pontificate of Innocent III (1198–1216) and financial accounts of the apostolic chamber under Nicholas III (1277–80). For the fourteenth century, there are new series of registers of outgoing letters (the Avignon Registers and the Lateran Registers) and a vast increase in the quantity of surviving records of the apostolic chamber. However, with the increasing abundance of such records, the proportion to have been published diminishes. It is in the fourteenth century that the sheer wealth of the surviving sources (there are, for instance, sixty registers of papal letters from the pontificate of Gregory XI, which lasted seven years and three months) first becomes a serious problem for those pursuing the publication of papal records.