@inproceedings{nils1994the,
title={The propagation of polarization for systems of transversal type},
author={Nils Dencker},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203545999218645},
booktitle={Arkiv for Matematik},
volume={33},
number={2},
pages={249-279},
year={1994},
}