@inproceedings{dorin2019maximization,
title={Maximization of the second non-trivial Neumann eigenvalue},
author={Dorin Bucur, and Antoine Henrot},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20191128120533199921543},
booktitle={Acta Mathematica},
volume={222},
number={2},
pages={337-361},
year={2019},
}
Dorin Bucur, and Antoine Henrot. Maximization of the second non-trivial Neumann eigenvalue. 2019. Vol. 222. In Acta Mathematica. pp.337-361. http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20191128120533199921543.