@inproceedings{kjell-ove1964on,
title={On the boundary values of harmonic functions in R^{3}},
author={Kjell-Ove Widman},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203430920946014},
booktitle={Arkiv for Matematik},
volume={5},
number={3},
pages={221-230},
year={1964},
}