BoichukО. A., E. V. Chuiko, and S. M. Chuiko. 1996. “Generalized Green Operator of a Boundary-Value Problem With Degenerate Pulse Influence”. Ukrains’kyi Matematychnyi Zhurnal 48 (5), 588-94. https://umj.imath.kiev.ua/index.php/umj/article/view/5291.