Il’kiv, V. S., I. I. Volyanska, and M. M. Symotyuk. 2018. “Nonlocal Boundary-Value Problem for a Second-order partial Differential Equation in an Unbounded Strip”. Ukrains’kyi Matematychnyi Zhurnal 70 (10), 1374-81. https://umj.imath.kiev.ua/index.php/umj/article/view/1641.