元末周德清最早对其作了详备的论述；
Towards the end of the Yuan Dynasty , Mr.
分析周德清的政治倾向，对于研究《中原音韵》所反映的元代语音情况有重要意义。
It is of great importance to analyse Zhou s political orientation because it serves as a necessary background to study the pronunciation in Yuan Dynasty expressed by Zhongyuanyinyun .
周德清