@inproceedings{bengt1953a,
title={A note on the constant of Koebe},
author={Bengt J. Andersson},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203416769066891},
booktitle={Arkiv for Matematik},
volume={2},
number={5},
pages={415-416},
year={1953},
}