@inproceedings{i.1954an,
title={An isoperimetric inequality for closed curves convex in even-dimensional euclidean spaces},
author={I. J. schoenberg},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203139388801793},
booktitle={Acta Mathematica},
volume={91},
number={1},
pages={143-164},
year={1954},
}
I. J. schoenberg. An isoperimetric inequality for closed curves convex in even-dimensional euclidean spaces. 1954. Vol. 91. In Acta Mathematica. pp.143-164. http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203139388801793.