《史记·七十列传·大宛列传》
张骞留居匈奴，匈奴对他的看护渐渐宽松，张骞因而得以同他的随从逃向月氏，向西跑了几十天，到达大宛。
居匈奴中，益宽，骞因与其属亡乡月氏，西走数十日至大宛。
While Zhang Qian dwelt among the Xiongnu, the Xiongnu relaxed their watch on him somewhat, so Zhang Qian and his companions escaped to Yuezhi, traveling westward for several tens of days to reach Dayuan.