@inproceedings{anders1970lower,
title={Lower bounds for pseudo-differential operators},
author={Anders Melin},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203446762832148},
booktitle={Arkiv for Matematik},
volume={9},
number={1},
pages={117-140},
year={1970},
}