@inproceedings{pavel2003spectral,
title={Spectral properties of Schrdinger operators with a strongly attractive delta interaction supported by a surface},
author={Pavel Exner},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20191020125201848054608},
booktitle={arXiv preprint math-ph/0301021},
year={2003},
}

Pavel Exner. Spectral properties of Schrdinger operators with a strongly attractive delta interaction supported by a surface. 2003. In arXiv preprint math-ph/0301021. http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20191020125201848054608.