Many examples of graffiti and inscriptions — largely of names and greetings — document the area of Nabataean culture, which extended as far north as the north end of the Dead Sea, and testify to widespread literacy; but no Nabataean literature has survived, nor was any noted in antiquity, and the temples bear no inscriptions. Onomastic analysis has suggested that the Nabataean culture may have embraced multiple ethnicities. Classical references to the Nabataeans begin with Diodorus Siculus; they suggest that the Nabataeans' trade routes and the origins of their goods were regarded as trade secrets, and disguised in tales that should have strained outsiders' credulity. Diodorus Siculus (book ii) described them as a strong tribe of some 10,000 warriors, pre-eminent among the nomads of Arabia