@article{Aalen2001,
author = {Aalen, O. and Borgan, Ø. and Fekjær, H.},
title= {Covariate Adjustment of Event Histories Estimated from Markov Chains: The Additive Approach},
year = {2001},
doi = {10.1111/j.0006-341X.2001.00993.x},
journal = {Biometrics},
volume = {57},
number = {4},
pages = {993--1001},
}