1. Lanzhou University; Evidence-Based Medicine Center, School of Basic Medical Sciences; No. 199, Donggang West Road Lanzhou City Gansu China 730000
2. Lanzhou University; Key Laboratory of Evidence Based Medicine and Knowledge Translation of Gansu Province; Lanzhou City China
3. University of Southern California; School of Social Work; 669 W. 34th St Los Angeles CA USA 90089-0411