Uusküla, Anneli, Lisa G. Johnston, Mait Raag, Aire Trummal, Ave Talu, and Don C. Des Jarlais. "Evaluating recruitment among female sex workers and injecting drug users at risk for HIV using respondent-driven sampling in Estonia." Journal of urban health : bulletin of the New York Academy of Medicine 87, no. 2 (2010): 304-17.