@article{Laird1981,
author = {Laird, N. and Olivier, D.},
title= {Covariance analysis of censored survival data using log-linear analysis techniques},
year = {1981},
doi = {10.1080/01621459.1981.10477634},
journal = {Journal of the American Statistical Association},
volume = {76},
number = {374},
pages = {231--240},
}