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Atlas of the World’s Languages in Danger . Christopher Moseley (ed.) (2010) · UNESCO Publishing http://www.unesco.org/culture/en/endangeredlanguages/atlas

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The Koch of Bangladesh: A Sociolinguistic Survey . Ahmad, Sayed and Kim, Amy and Kim, Seung and Sangma, Mridul (2011) · http://www.sil.org/resources/publications/entry/41580