Complex sentence: At first the Salians lived between the Rhine and the IJssel in the modern day Dutch region of the Veluwe, Gelderland, where they are believed to have given their name to the region of Salland.
Split into simpler sentences: At first the Salians lived between the Rhine and the IJssel in the modern day Dutch region of the Veluwe, Gelderland. They are believed to have given their name to the region of Salland.