@article{Hougaard1984,
author = {Hougaard, P.},
title= {Life table methods for heterogeneous populations: Distributions describing the heterogeneity},
year = {1984},
doi = {10.1093/biomet/71.1.75},
journal = {Biometrika},
volume = {71},
number = {1},
pages = {75--83},
}