Comparing Provider and Client Preferences for HIV Prevention Services in South Africa among Men Who Have Sex with Men oleh John Shaver, Patrick Sullivan PhD, DVM, Aaron Siegler PhD, Alex de Voux PhD, Nancy Phaswana-Mafuya PhD, Linda-Gail Bekker PhD, Stefan D. Baral MD, Andrea L. Wirtz PhD, Chris Beyrer MD, Ben Brown, Rob Stephenson PhD