@article{Petersen2006,
author = {Petersen, M.L. and Sinisi, S.E. and van der Laan, M.J.},
title= {Estimation of direct causal effects},
year = {2006},
doi = {10.1097/01.ede.0000208475.99429.2d},
journal = {Epidemiology},
volume = {17},
number = {3},
pages = {276--284},
}