One other train besides the one to Lhasa goes to Xining. Though getting train tickets to Lhasa could be a problem.
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jannekewaninge
We are also planning for a tour from Chengdu to Tibet and back for the 10th of Oktober. And we are looking for travel companions, to share the costs. See also my post at
http://www.lonelyplanet.com/thorntree/thread.jspa?threadID=1966348
Pro tip