%0 Journal Article %T Identification and Efficient Estimation of the Natural Direct Effect among the Untreated %A Lendle, Samuel D. %A Subbaraman, Meenakshi S. %A van der Laan, Mark J. %J Biometrics %V 69 %N 2 %P 310-317 %@ 0006-341X %D 2013-06-01 %I Wiley Subscription Services, Inc., A Wiley Company %~ DeepDyve