由于进入该地区需要官方的许可，只有很少的语言学家在这个地区工作，而且关于这一地区的语言从未形成一个可靠的清单列表。
A permit is required to visit, few linguists have worked there and a reliable list of languages has never been drawn up.
由于进入该地区需要官方的许可，只有很少的语言学家在这个地区工作，而且关于这一地区的语言从未形成一个可靠的清单列表。
A permit is required to visit, few linguists have worked there and a reliable list of languages has never been drawn up.
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