@article{Yau1998,
author = {Yau, K.K.W. and McGilchrist, C.A.},
title= {ML and REML estimation in survival analysis with time dependent correlated frailty},
year = {1998},
doi = {10.1002/(sici)1097-0258(19980615)17:11<1201::aid-sim845>3.0.co;2-7},
journal = {Statistics in Medicine},
volume = {17},
number = {11},
pages = {1201--1213},
}