1. The shifted of the sound changes phenomena in Shandong district proves that Round-mouth characters of Zhi-system read in labiodental firstly occur in fricative.
由这种音变现象在山东地区的地域流变情况可见，知系合口字的唇齿化有可能首先发生于擦音声母。
来自互联网
2. The shifted of the sound changes phenomena in Shandong district proves that Round-mouth characters of Zhi-system read in labiodental firstly occur in fricative.
