To determine the actual usage of the hymn or sequence rather than its mere existence as a specimen of religious verse, the liturgical collection is indispensable. The old hymnaries and psalters and other books used in the offices were examined by liturgists of the period who compiled the breviaries of the later Middle Ages. Working under episcopal or monastic authority they subjected the hymnic material at their disposal to a selective process which necessarily discarded many hymns in favor of those rendered sacred by their inclusion in the old cycles, or of hymns of recognized merit. The Mozarabic Breviary had been compiled and its hymns determined by this process in an earlier century. After the re-conquest of the Spanish peninsula and the introduction of the Roman Rite in 1089, a version of the Roman Breviary was introduced. Episcopal centers in England, such as Hereford, York and primarily Salisbury, compiled their service books and developed them continuously to the close of the Middle Ages. The process was repeated throughout Christian Europe. From the troparies and local collections of sequences the selections for the gradual and missal were made, just as the hymns had been for the breviary. These liturgical sources offer to the modern student the range of medieval hymnody at its best. The episcopal rites are, perhaps, more official and authoritative in their selection of hymns and sequences but the monastic rites often reveal the legends of local saints or the more intimate flavor of traditional piety. It should be understood that in countries where the Roman Rite prevailed there was no departure from its authority in the matter of hymnody. At the same time the greatest latitude was observable. A fine illustration is provided by the books of the Rite of Salisbury, England, or the Sarum Rite, which were compiled and developed by great liturgists from the time of Bishop Osmund in the eleventh century to the close of the Middle Ages. The Sarum Breviary contains 119 hymns, 25 of which were written after 1100 and the Missal contains 101 sequences, 54 of which were written about 1100.[12] The figures are revealing in the case of hymns, of the influence of the older cycles and in the case of sequences, of the multiplication of feasts in the later centuries of the Middle Ages.