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Prior to the emergence of the Tibetan diaspora in the 1950s , Tibetans do not seem to have been familiar with abortion for reasons of medical necessity , and , facing little population pressure , saw little reason to engage in what they saw as the destruction of innocent life .
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Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
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