The frontiers of the Moravian state under Mojmir I are not precisely known. It is, however, certain that the Moravians were expanding in the 830s. By the time the document known as the "Catalogue of Fortresses and Regions to the North of the Danube" was compiled sometime between 844 and 862, the Moravians already held eleven fortresses in the region. Similarly, the "Conversion of the Bavarians and the Carantanians", an historical work written in 870, relates that around 833 a local Slavic ruler, Pribina, was "driven across the Danube by Mojmir, duke of the Moravians". Pribina was either the head of another Slavic principality or one of Mojmir I's rebellious subordinates. Modern historians, although not unanimously, identify Pribina's lands ""in Nitrava ultra Danubium"" with modern Nitra (Slovakia).