@inproceedings{arne1962a,
title={A theorem on duality mappings in Banach spaces},
author={Arne Beurling, and A. E. Livingston},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203427541100986},
booktitle={Arkiv for Matematik},
volume={4},
number={5},
pages={405-411},
year={1962},
}
Arne Beurling, and A. E. Livingston. A theorem on duality mappings in Banach spaces. 1962. Vol. 4. In Arkiv for Matematik. pp.405-411. http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203427541100986.