@article{Gray1990,
author = {Gray, R.H. and Campbell, O.M. and Apelo, R. and Eslami, S.S. and Zacur, H. and Ramos, R.M. and Labbok, M.H.},
title= {Risk of ovulation during lactation},
year = {1990},
doi = {10.1016/0140-6736(90)90147-W},
URL = {https://doi.org/doi:10.1016/0140-6736(90)90147-W},
volume = {335},
number = {8680},
pages = {25‒29},
}