@inproceedings{denis2006distant,
title={Distant perturbation asymptotics in window-coupled waveguides. I. The nonthreshold case},
author={Denis Borisov, and Pavel Exner},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20191020131051673807666},
booktitle={Journal of mathematical physics},
volume={47},
number={11},
pages={113502},
year={2006},
}

Denis Borisov, and Pavel Exner. Distant perturbation asymptotics in window-coupled waveguides. I. The nonthreshold case. 2006. Vol. 47. In Journal of mathematical physics. pp.113502. http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20191020131051673807666.