DeMets DL, Fleming TR, Whitley RJ, Childress JF, Ellenberg SS, Foulkes M, Mayer KH, O'Fallon J, Pollard RB, Rahal JJ, et al. The data and safety monitoring board and acquired immune deficiency syndrome (AIDS) clinical trials. Control Clin Trials. 1995 Dec; 16(6):408-21.