@inproceedings{makoto1990regularity,
title={Regularity of a boundary having a Schwarz function},
author={Makoto Sakai},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203316343358457},
booktitle={Acta Mathematica},
volume={166},
number={1},
pages={263-297},
year={1990},
}