There are Indian literary sources, ranging from the Milinda Panha, a dialogue between a Buddhist sage Nagasena and Indianized names that may be related to Indo-Greek kings such as Menander I. Names in these sources are consistently Indianized, and there is some dispute whether, for example, Dharmamitra represents "Demetrius" or is an Indian prince with that name. There was also a Chinese expedition to Bactria by Chang-k'ien under the Emperor Wu of Han, recorded in the Records of the Grand Historian and Book of the Former Han, with additional evidence in the Book of the Later Han; the identification of places and peoples behind transcriptions into Chinese is difficult, and several alternate interpretations have been proposed. Other evidence of the broader and longer influence of Indo-Greeks is possibly suggested by Yavanarajya inscription, dated to the 1st-century BC. It mentions Yavanas, a term which is derived from "Ionians", and which at that time most likely means "Indo-Greeks". Expansion of Demetrius into India Demetrius I, the son of Euthydemus is generally considered the Greco-Bactrian king who first launched the Greek expansion into India. He is therefore the founder of the Indo-Greek realm. The true intents of the Greek kings in occupying India are unknown, but it is thought that the elimination of the Maurya Empire by the Sunga greatly encouraged this expansion. The Indo-Greeks, in particular Menander I who is said in the Milindapanha to have converted to Buddhism, also possibly received the help of Indian Buddhists. There is an inscription from his father's reign already officially hailing Demetrius as victorious. He also has one of the few absolute dates in Indo-Greek history: after his father held off Antiochus III for two years, 208–6 BC, the peace treaty included the offer of a marriage between Demetrius and Antiochus' daughter. Coins of Demetrius I have been found in Arachosia and in the Kabul Valley; the latter would be the first entry of the Greeks into India, as they defined it. There is also literary evidence for a campaign eastward against the Seres and the Phryni; but the order and dating of these conquests is uncertain. Demetrius I seems to have conquered the Kabul valley, Arachosia and perhaps Gandhara; he struck no Indian coins, so either his conquests did not penetrate that far into India or he died before he could consolidate them. On his coins, Demetrius I always carries the elephant-helmet worn by