@inproceedings{eric1967generalized,
title={Generalized hyperbolicity},
author={Eric Larsson},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203437460173069},
booktitle={Arkiv for Matematik},
volume={7},
number={1},
pages={11-32},
year={1967},
}