Some Questions on Overlapped Sound Change Theory

Overlapped sound change theory regard as a special sound change type of discrete sound change put forward by Prof.Xu Tong-qiang(徐通锵)have certain theory meanings.But its explanations such as the reason of sound change with variant pronunciation in literary and colloquial readings, distinguishing the way competition and change in the process of sound change,and difference between overlapped sound change and discrete sound change,also need to discuss further.