Baseline characteristics and statistical power in randomized controlled trials: selection, prognostic targeting, or covariate adjustment?
Roozenbeek B, Maas AI, Lingsma HF, Butcher I, Lu J, Marmarou A, McHugh GS, Weir J, Murray GD, Steyerberg EW, et al. Crit Care Med. 2009 Oct; 37(10):2683-90.