That Pergamon probably paid tribute can be inferred from Livy 38.16, that the Gauls had "... levied tribute on the whole of Asia west of the Taurus, ... such was the terror of their name and the growth of their numbers that at last even the kings of Syria did not dare to refuse the payment of tribute" and that Attalus I, Eumenes successor, was the first to refuse to pay such tribute.
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Strabo 13.4.2, says that Eumenes "... died after a reign of twenty-two years." His reign began with the death of Philetaerus in 263 BC.
Strabo, 13.4.2, says that he was the cousin of Attalus I. Pausanias, 1.8.1, probably following Strabo, says the same. But modern writers have concluded that Strabo had skipped a generation, see Hansen p. 26.
