@article{Pongou2013,
author = {Pongou, r.},
title= {Why is infant mortality higher in boys than in girls? A new hypothesis based on preconception environment and evidence from a large sample of twins},
year = {2013},
doi = {10.1007/s13524-012-0161-5},
journal = {Demography},
volume = {50},
number = {2},
pages = {421--444},
}