1. Department of E.N.T, Gansu Provincial Hospital, Lanzhou, P.R. China
2. The First School of Clinical Medicine, Gansu University of Chinese Medicine, Lanzhou, P.R. China
3. The First School of Clinical Medicine, Lanzhou University, Lanzhou, P.R. China
4. Department of Clinical Medicine, Ningxia Medical University, Yinchuan, P.R. China