Kengne, E. “On the Well-Posedness of a Two-Point Boundary-Value Problem for a System With Pseudodifferential Operators”. Ukrains’kyi Matematychnyi Zhurnal, vol. 57, no. 8, Aug. 2005, pp. 1131 – 1136, https://umj.imath.kiev.ua/index.php/umj/article/view/3671.