@article{Luo2004,
author = {Luo, Z.C. and Wilkins, R. and Kramer, M.S.},
title= {Disparities in pregnancy outcomes according to marital and cohabitation status},
year = {2004},
journal = {Obstetrics and Gynecology },
volume = {103},
number = {6},
pages = {1300--1307},
}