S. Strathdee and J. K. Stockman, “Epidemiology of HIV among Injecting and Non-Injecting Drug Users: Current Trends and Implications for Interventions,” Current HIV/ AIDS Reports, Vol. 7, No. 2, 2010, pp. 99-106.
 J. A. Inciardi, “Crack, Crack House Sex, and HIV Risk,” Archives of Sexual Behavior, Vol. 24, No. 3, 1995, pp. 249-269.
 M. Ratner, “Sex, Drugs, and Public Policy: Studying and Understanding the Sex-For-Crack Phenomenon,” In: M. Ratner, Ed., Crack Pipe as Pimp: An Ethnographic Investigation of Sex-for-Crack Exchanges, Lexington Books, New York, 1993.
 D. Jones, et al., “The High-Risk Sexual Practices of CrackSmoking Sex Workers Recruited from the Streets of Three American Cities,” Sexually Transmitted Diseases, Vol. 25, No. 4, 1998, pp. 187-193.
 J. A. Inciardi, “Kingrats, Chicken Heads, Slow Necks, Freaks, and Blood Suckers: A Glimpse at the Miami SexFor-Crack Market,” In: M. Ratner, Ed., Crack Pipe as Pimp: An Ethnographic Investigation of Sex-for-Crack Exchanges, Lexington Books, New York, 1993.
 P. Bourgois and E. Dunlap, “Exorcising Sex-For-Crack: An Ethnographic Perspective from Harlem,” In: M. Ratner, Ed., Crack Pipe as Pimp: An Ethnographic Investigation of Sex-fro-Crack Exchanges, Lexington Books, New York, 1993.
 J. Dickson-Gomez, “Structural Factors Influencing Patterns of Drug Selling and Use in the San Salvador Metropolitan Area,” Medical Anthropology Quarterly, Vol. 24, No. 2, 2010, pp. 157-181.
 J. Dickson-Gomez, et al., “With God’s Help I Can Do It: Crack Users’ Formal and Informal Recovery Experiences in El Salvador,” Substance Use and Misuse, Vol. 46, No. 4, 2010, pp. 426-439.
 J. Dickson-Gomez, et al., “The Relationship between Community Structural Characteristics, the Context of Drug Use, and HIV Risk Behaviors in San Salvador, El Salvador,” Substance Use and Misuse, Vol. 47, No. 3, 2012, pp. 265-277.
 D. D. Heckathorn and R. Magnani, “Snowball and Respondent-Driven Sampling,” In: Behavioral Surveillance Surveys: Guidelines for Repeated Behavioral Surveys in Populations at Risk of HIV, in Press.
 D. D. Heckathorn, et al., “Extensions of Respondent Driven Sampling: A New Approach to the Study of Injection Drug Users Aged 18-25,” AIDS and Behavior, Vol. 6, No. 1, 2002, pp. 55-67.
 M. Castells and A. Portes, “World Underneath: The Origins, Dynamics, and Effects of the Informal Economy,” In: A. Portes, M. Castells and L. Benton, Eds., The Informal Economy: Studies in Advanced and Less Developed Countries, Johns Hopkins University Press, Baltimore, 1989.
 S. D. Pinkerton and P. R. Abramson, “Effectiveness of Condoms in Preventing HIV Transmission,” Social Science and Medicine, Vol. 44, No. 19, 1997, pp. 13031312. http://dx.doi.org/10.1016/S0277-9536(96)00258-4
 J. Dickson-Gomez, et al., “Crack Use Sites and HIV in El Salvador,” Journal of Drug Issues, Vol. 37, No. 2, 2007, pp. 445-476.
 J. Dickson-Gomez, et al., “Resources and Obstacles to Developing and Implementing a Structural Intervention to Prevent HIV in San Salvador, El Salvador,” Social Science and Medicine, Vol. 70, No. 3, 2010, pp. 351-359.
 B. Van Der Pol, et al., “Trichomonosas Vaginalis Infection and Human Immunodeficiency Virus Acquisition in African Women,” Journal of Infectious Diseases, Vol. 197, No. 4, 2008, pp. 548-554.
 H. Burris, et al., “Getting Research into Policy—Herpes Simplex Virus Type-2 (HSV-2) Treatment and HIV Infection: International Guidelines Formulation and the Case of Ghana,” Health Research Policy Systems, Vol. 9, Suppl. 1, 2011, p. S5.