@article{Box-Steffensmeier2006,
author = {Box-Steffensmeier, J.M. and De Boef, S. and Joyce, K.A.},
title= {Event dependence and heterogeneity in duration models: The conditional frailty model},
year = {2006},
doi = {10.1093/pan/mpm013},
journal = {Political Analysis},
volume = {15},
number = {3},
pages = {237‒256},
}