In the 19th and early 20th century, Pavel Jozef Šafárik and Lubor Niederle combined both Western and Eastern concept on the localization of Croatia, specifically, to be extending from Eastern Galicia up to Northeastern Bohemia. Niederle argued that they mainly were located on river Vistula, between Czech and Ukrainian Croats, and they formed one big alliance of Croatian tribes which fell apart when the Vistulan Croats migrated to the Western Balkans in the 7th century. Josef Markwart and Ljudmil Hauptmann also placed their main center on river Vistula. The Polish historians mostly were against the localization of Croatian homenland on river Vistula (eventually in Silesia), arguing it is based on loose evidence, and as such ignored Croats and White Croatia in their synthesis of the Polish history. It was in accordance with Czech and German historians who related it with the principality of Slavník dynasty on Upper Elbe river in Northeastern Bohemia, and considered that those Croats came from Ukrainian Croats on river Dniester, which argued Ukrainian and Russian historians.