Interlaboratory comparison study of serum total testosterone measurements performed by mass spectrometry methods - Vesper, H W; Bhasin, S; Wang, C; Tai, S S; Dodge, L A; Singh, R J; Nelson, J; Ohorodnik, S; Clarke, N J; Salameh, W A; Parker, C R, Jr; Razdan, R; Monsell, E A; Myers, G L (Steroids, 2009)