chronicling Magyar battles with local rulers (including Gelou, Menumorut and Salan) not mentioned in other primary sources. Transylvania on the eve of the Hungarian conquest The nomadic Avars dominated the Carpathian Basin from about 567. In Transylvania, archaeological evidence attributed to them around 630 is clustered in the region of the salt mines at Ocnișoara, Ocna Mureș and Turda, and along the rivers Mureș and Someș. The cremation cemeteries of the Mediaș group, a sedentary population, were also concentrated around the salt mines in the seventh to ninth centuries. Although the Mediaș cemeteries have been attributed to Slavs, according to Madgearu "the presence of Romanians in this context should not be ruled out". The names of many rivers in Transylvaniafor instance, Bistrița ("swift"), Cerna ("black"), Dobra ("good") and Târnava ("thorny")are of Slavic origin, indicating the historical presence of a Slavic-speaking population. According to Madgearu, two eighth-century spurs unearthed at Șura Mică and Medișoru Mare "suggest the existence of cavalry troops of Slavs and, perhaps, Romanians in Avar service" (since Avar spur use is uncertain). The Avar Khaganate disintegrated after the Franks invaded its western regions three times between 791 and 803. A stone column erected during the reign of Omurtag of Bulgaria commemorates the 829 death of a Bulgarian commander named Onegavon at the river Tisa, indicating that the Bulgarians invaded the eastern regions of the one-time khaganate. According to the Annals of Fulda, in 894 Emperor Arnulf sent envoys to the Bulgarians to "ask that they should not sell salt to the Moravians"; this demonstrates that the Bulgarians controlled, at a minimum, the roads between the Transylvanian salt mines and Moravia. According to Kurdt Horedt, István Bóna and other historians, Dridu B pottery unearthed in the Alba Iulia region which was similar to ceramic utensils found along the lower Danube demonstrates that the Bulgarians expanded their authority over this region. Other historians (including Victor Spinei) reject this theory, saying that Dridu B ceramics can only prove cultural influences from the Balkan Peninsula. The so-called "Ciumbrud group" of cemeteries, which were also unearthed near Alba Iulia, yielded earrings and clothing accessories analogous to finds from the lower Danube region and Moravia. Spurs, weapons and other Frankish objects unearthed at Iernut, Tărtăria and other Transylvanian sites demonstrate ninth-century trade with the Carolingian Empire; similar spurs were also commonly used in Bulgaria and by 10th-century Magyars. According to historians Vlad Georgescu, Ioan-Aurel