@article{Chao2019,
author = {Chao, F. and Gerland, P. and Cook, A.R. and Alkema, L.},
title= {Systematic assessment of the sex ratio at birth for all countries and estimation of national imbalances and regional reference levels},
year = {2019},
doi = {10.1073/pnas.1812593116},
volume = {116},
number = {19},
pages = {9303--9311},
}