@article{Coall2009,
author = {Coall, D.A. and Meier, M. and Hertwig, R. and Wänke, M. and Höpflinger, F.},
title= {Grandparental Investment: The Influence of Reproductive Timing and Family Size},
year = {2009},
doi = {10.1002/ajhb.20894},
journal = {American Journal of Human Biology},
volume = {21},
number = {4},
pages = {455--463},
}