Buchbinder SP, Mehrotra DV, Duerr A, Fitzgerald DW, Mogg R, Li D, Gilbert PB, Lama JR, Marmor M, Del Rio C, McElrath MJ, Casimiro DR, Gottesdiener KM, Chodakewitz JA, Corey L, Robertson MN; Step Study Protocol Team.
Lancet. 2008 Nov 29;372(9653):1881-93. Epub 2008 Nov 13.