Cosmas of Prague
In the West, in the mid-10th century, Al-Masudi mentioned them as Dūlāba and their "king" (ruler) as Wānjslāf (most probably Wenceslaus I, Duke of Bohemia). According to chronicle by Cosmas of Prague (12th century), fortified settlement Doudleby, which exists even today, was part of Slavník's territory in the South Bohemian Region.