@inproceedings{bengt1964on,
title={On the probabilities that a random walk is negative},
author={Bengt Rosén},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203431802313022},
booktitle={Arkiv for Matematik},
volume={5},
number={3},
pages={317-325},
year={1964},
}