M. F. Silveira, C. L. Alves, V. M. A. Brum, A. M. F. Teixeira, R. M. Rosenthal, and D. Stauffert, “Knowledge about HIV and syphilis serologic status among sex workers from Pelotas, Brazil”, DST, vol. 21, no. 1, pp. 27–33, Jan. 2009.