1. Department of Neurosurgery, Central Hospital Affiliated to Shandong First Medical University, Jinan, Shandong Province, P. R. China
2. Department of Neurosurgery, Liaocheng People's Hospital and Liaocheng Brain Hospital, Liaocheng, Shandong Province, P. R. China
3. Department of Stomatology, Dongying District People's Hospital, Dongying, Shandong Province, P. R. China
4. Department of Neurosurgery, Shengli Oilfield Central Hospital, Dongying, Shandong Province, P. R. China