@inproceedings{yngve1968an,
title={An extremal problem related to Kolmogoroff’s inequality for bounded functions},
author={Yngve Domar},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203440662641097},
booktitle={Arkiv for Matematik},
volume={7},
number={5},
pages={433-441},
year={1968},
}

Yngve Domar. An extremal problem related to Kolmogoroff’s inequality for bounded functions. 1968. Vol. 7. In Arkiv for Matematik. pp.433-441. http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203440662641097.