Mikhailets, V. A., and T. B. Skorobohach. “Fredholm Boundary-Value Problem in Sobolev – Slobodetsky Spaces”. Ukrains’kyi Matematychnyi Zhurnal 73, no. 7 (July 20, 2021): 920 - 930. Accessed August 12, 2022. http://umj.imath.kiev.ua/index.php/umj/article/view/6684.