1. a Department of Public Health , School of Medicine, National Cheng Kung University , Tainan , Taiwan
2. b Department of Community Health Sciences , School of Public Health, University of California at Los Angeles , California , US
3. c Center for Urban Initiatives and Research , Milwaukee , WI , US
4. d Department of Psychiatry , University of California at San Francisco , California , US
5. e San Francisco General Hospital , San Francisco , California , US
6. f AIDS Prevention Program , College of Health and Urban Affairs/Public Health, Florida International University , Florida , US