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Raiding and brigandage were rife in Mesopotamia at this period , and the creation of a new East Syrian metropolitan province reflected a migration of Christians from the Tigris plains to the relative safety of Adarbaigan , where there was a strong Mongol military presence .
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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:
 None