1. The Carman and Ann Adams Department of Pediatrics Prevention Research Center, Wayne State University, Detroit, Michigan.
2. Beijing Normal University, Institute for Developmental Psychology, Beijing, China, E-mail: fangxy@bnu.edu.cn
3. Department of Epidemiology, National Center for STD and Leprosy Control, Nanjing, China.
4. National Center for AIDS/STD Prevention and Control, China Center for Diseases Prevention and Control, Beijing, China.
5. Beijing Normal University Institute of Developmental Psychology, Beijing, China.