1. Friends Research Institute, Center for HIV Identification, Prevention and Treatment Services, University of California, Los Angeles, Los Angeles, California, USA
2. Department of Psychiatry and Biobehavioral Sciences, Semel Institute for Neuroscience and Human Behavior, University of California, Los Angeles, Los Angeles, California, USA
3. Integrated Substance Abuse Programs, Semel Institute for Neuroscience and Human Behavior, University of California, Los Angeles, Los Angeles, California, USA
4. University of Medicine and Pharmacy, Ho Chi Minh City, Vietnam