The map shows the frontier between the Central Tibet ('Outer Tibet') and Eastern Tibet ('Inner Tibet') as decided at the <a href="https://en.wikipedia.org/wiki/Simla_Convention" class="extiw" title="w:Simla Convention">1914 Simla Conference</a> and the actual frontier that was in effect during various parts of the early 20th century.
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From the Legend:
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<ul><li>bold red line - frontier of the Tibet region</li>
<li>bold blue line - boundary between Outer Tibet and Inner Tibet proposed in the Simla Conference</li>
<li>dotted blue line - boundary during the Qing Empire 1727-1910</li></ul><hr><ul><li>light blue line - de facto boundary during 1912-1917</li>
<li>dark brown line - de facto boundary during 1918-1932</li>
<li>dotted red line - de facto boundary in 1945</li></ul>
Hugh Richardson
1945
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