@inproceedings{pavel2011vertex,
title={Vertex couplings in quantum graphs: approximations by scaled Schrdinger operators},
author={Pavel Exner},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20191020133114438862729},
booktitle={Proceedings of the ICM Satellite Conference Mathematics in Science and Technology (New Delhi 2010},
pages={71-92},
year={2011},
}

Pavel Exner. Vertex couplings in quantum graphs: approximations by scaled Schrdinger operators. 2011. In Proceedings of the ICM Satellite Conference Mathematics in Science and Technology (New Delhi 2010. pp.71-92. http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20191020133114438862729.