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In page Sino-Tibetan languages:

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Several low-level branches of the family, particularly Lolo-Burmese, have been securely reconstructed, but in the absence of a secure reconstruction of a Sino-Tibetan proto-language, the higher-level structure of the family remains unclear.[1][2] Thus, a conservative classification of Sino-Tibetan/Tibeto-Burman would posit several dozen small coordinate families and isolates; attempts at subgrouping are either geographic conveniences or hypotheses for further research.[citation needed]