`  == ``Historians argue that China and Tibet remained two separate units`` ==  Hi there. Are you sure that sentence (which you added to Amdo) appears in the source cited? (The Story of Tibet: Conversations with the Dalai Lama, by Thomas Laird, Grove Press, 2006, ISBN 0802118275)  I couldn't find it in there. Could you give me a pinpoint (i.e. page) reference?  The same sentence appears in History of Tibet, where it is tagged ``Citation needed``. If you can give me a pinpoint citation for the sentence, it should also be added to that article.   `