The Li Lao culture flourished from approximately 200 to 750 AD in present day Southern China and Northern Vietnam. These Li tribes were recorded in Chinese sources as Lǐ (俚) "bandits" inhabiting the coastal areas between the Pearl River and Red River. Li political structures were distributed in numerous autonomous settlements/chiefdoms (dong 洞) located in riverine valleys. The Book of Sui notes that Li noblemen who possess bronze drum in each dong were called dulao (都老), which Churchman argues bears some resemblance and cultural connection to the previous local ruling class of the Red River Delta. The Li tribes were described as ferocious raiding bandits who refused to accept imperial authority, leading to Jiaozhou, the heartland of the Red River Delta, whence the Chinese deemed a lone, isolated borderlands with difficult, limited administration. Because the Li-Lao people managed to keep themselves away from Chinese sphere of cultural influence, the landscape of Northern Vietnam during Han-Tang period experienced a perfect equilibrium between Sinification and localization. From the sixth to the seventh century, Chinese dynasties attempted to militarily subdue the Li dong, gradually causing the Li Lao culture to decline.