@article{1177013233,
author = {Holland, Paul W.},
title = {[The Role of a Second Control Group in an Observational Study]: Comment},
journal = {Statist. Sci.},
volume = {2},
number = {4},
year = {1987},
pages = { 306-308},
language = {en},
url = {http://dml.mathdoc.fr/item/1177013233}
}
Holland, Paul W. [The Role of a Second Control Group in an Observational Study]: Comment. Statist. Sci., Tome 2 (1987) no. 4, pp. 306-308. http://gdmltest.u-ga.fr/item/1177013233/