Their trade, with some interruptions, continued in the 9th century within the framework of the Uighur Empire, which until 840 extended across northern Central Asia and obtained from China enormous deliveries of silk in exchange for horses. At this time caravans of Sogdians traveling to Upper Mongolia are mentioned in Chinese sources. They played an equally important religious and cultural role. Part of the data about eastern Asia provided by Muslim geographers of the 10th century actually goes back to Sogdian data of the period 750–840 and thus shows the survival of links between east and west. However, after the end of the Uighur Empire, Sogdian trade went through a crisis. What mainly issued from Muslim Central Asia was the trade of the Samanids, which resumed the northwestern road leading to the Khazars and the Urals and the northeastern one toward the nearby Turkic tribes.