@article{Gibson2003,
author = {Gibson, M.A. and Mace, R. },
title= {Strong mothers bear more sons in rural Ethiopia},
year = {2003},
doi = {10.1098/rsbl.2003.0031},
journal = {Proceedings of the Royal Society of London Series B },
volume = {270},
number = {Supplement},
pages = {108--109},
}