@inbook{Willekens2011a,
author = {Willekens, F.},
title= {Population accounts},
year = {2011a},
editor = {Stillwell, J.},
editor = {Clarke, M.},
booktitle = {Population dynamics and projection methods. Understanding Population Trends and Processes},
address = {Dordrecht, Netherlands},
publisher = {Springer},
pages = {29--40},
}