TY - STAND AU - R. Platt AU - J. Delaney AU - S. Suissa BT - Eur J Epidemiol DO - 10.1007/s10654-011-9637-7 M1 - 2 PY - 2012 SP - 77 EP - 83 T2 - Eur J Epidemiol TI - The positivity assumption and marginal structural models: the example of warfarin use and risk of bleeding VL - 27 SN - 0393-2990 ER -