@article{Zhang2004,
author = {Zhang, W. and Steele, F.},
title= {A semiparametric multilevel survival model},
year = {2004},
doi = {10.1111/j.1467-9876.2003.05056.x},
journal = {Journal of the Royal Statistical Society (Series C)},
volume = {53},
pages = {387--404},
}