@article{Vaupel2014,
author = {Vaupel, J.W. and Missov, T.I.},
title= {Unobserved population heterogeneity: A review of formal relationships},
year = {2014},
doi = {10.4054/DemRes.2014.31.22},
volume = {31},
number = {2},
pages = {659--686},
}