@article{El-Sayed2012,
author = {El-Sayed, A.M. and Tracy, M. and Galea, S.},
title= {Life course variation in the relation between maternal marital status and preterm birth},
year = {2012},
doi = {10.1016/j.annepidem.2012.01.002},
journal = {Annals of Epidemiology},
volume = {22},
number = {3},
pages = {168--174},
}