@article{Royston2002,
author = {Royston, P. and Parmar, M.K.B.},
title= {Flexible parametric proportional-hazards and proportional-odds model for censored survival data, with application to prognostic modeling and estimation of treatment effects},
year = {2002},
doi = {10.1002/sim.1203},
volume = {21},
number = {15},
pages = {2175--2197},
}