@inproceedings{pavel2018aharonov,
title={Aharonov and Bohm versus Welsh eigenvalues},
author={Pavel Exner, and Sylwia Kondej},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20191020134508289409771},
booktitle={Letters in mathematical physics},
volume={108},
number={9},
pages={2153-2167},
year={2018},
}

Pavel Exner, and Sylwia Kondej. Aharonov and Bohm versus Welsh eigenvalues. 2018. Vol. 108. In Letters in mathematical physics. pp.2153-2167. http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20191020134508289409771.