@article{Preston2012,
author = {Preston, S.H. and Stokes, A.},
title= {Sources of population aging in more and less developed countries},
year = {2012},
doi = {10.1111/J.1728-4457.2012.00490.X},
URL = {http://dx.doi.org/10.1111/J.1728-4457.2012.00490.X},
volume = {38},
number = {2},
pages = {221--236},
}