1. Division of Prevention and Community Research, Yale School of Medicine, New Haven, CT, USA
2. School of Public Administration, Hunan University, Changsha, Hunan, China
3. Department of Social Medicine and Health Management, Xiangya School of Public Health, Central South University, Changsha, Hunan, China
4. Department of Midwifery, Xiangya School of Nursing, Central South University, Changsha, Hunan, China