@article{Lewis1991,
author = {Lewis, P. and Brown, J. and Renfree, M. and Short, R.},
title= {The resumption of ovulation and menstruation in a well-nourished population of women breastfeeding for an extended period of time},
year = {1991},
doi = {10.1016/S0015-0282(16)54180-6},
volume = {55},
number = {3},
pages = {529--536},
}