@article{Christensen2009,
author = {Christensen, K. and Doblhammer, G. and Rau, R. and Vaupel, J.W.},
title= {Ageing populations: The challenges ahead},
year = {2009},
doi = {10.1016/S0140-6736(09)61460-4},
journal = {Lancet},
volume = {374},
number = {9696},
pages = {1196--1208},
}