Dudkin MY. Point spectrum of the schrödinger operator with point interactions at the vertices of regular <em class="a-plus-plus">N</em>-gons. Ukr. Mat. Zhurn. [Internet]. 2004Aug.25 [cited 2024May2];56(8):1128–1134. Available from: https://umj.imath.kiev.ua/index.php/umj/article/view/3827