@inproceedings{edgar1958metric,
title={Metric criteria of normality for complex matrices of order less than 5},
author={Edgar Asplund},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203422534660941},
booktitle={Arkiv for Matematik},
volume={3},
number={5},
pages={441-447},
year={1958},
}
Edgar Asplund. Metric criteria of normality for complex matrices of order less than 5. 1958. Vol. 3. In Arkiv for Matematik. pp.441-447. http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203422534660941.