@article{Coall2009,
author = {Coall, D.A. and Meier, M. and Hertwig, R. and Wanke, M. and Hopflinger, 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},
}