Old Church Slavonic is the name given to the language that is preserved in several manuscripts and a few inscriptions originating from the regions of the Moravian Empire, situated between the Vistula River and the easternmost extent of Carolingian influence, and the Bulgarian Empire, extending from the lower reaches of Macedonia in the south up beyond the Danube in the north. These are the regions of the first missionary work among the Slavs by the monks Cyril and Methodius, who devised in the 9th century AD the first full-fledged writing system to represent the indigenous language. The documents that survive are primarily ecclesiastical. They were produced in a religious tradition that used Old Church Slavonic as the liturgical medium very much the way Latin was used in the Roman Catholic Church.