Researchers studying strata in the phonological history of Chinese dialects should note the following: First, some historical strata emerged because of language contact. Second, beside the evolution of phonological categories themselves, it is also important to trace the actual sound change from one pronunciation to another. Third, primary (i.e. covering most characters in a category) and secondary strata should be differentiated, and the latter should not be blown out of proportion. Fourth, researchers should find out how the various strata in a dialect constitute a single synchronic system. The four points in discussion are all illustrated with examples from Min dialects.
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