@article{Brant1990,
author = {Brant, Rollin},
title= {Assessing Proportionality in the Proportional Odds Model for Ordinal Logistic Regression},
year = {1990},
doi = {10.2307/2532457},
journal = {Biometrics},
volume = {46},
number = {4},
pages = {1171--1178},
}