@article{Sear2001,
author = {Sear, R. and Mace, R. and Shanley, D. and McGregor, I.A.},
title= {The fitness of twin mothers: evidence from rural Gambia},
year = {2001},
doi = {10.1046/j.1420-9101.2001.00287.x},
journal = {Journal of Evolutionary Biology},
volume = {14},
number = {3},
pages = {433--443},
}