BritovN. A. “On the Triviality Condition for the Kernel of the Linearized First Boundary-Value Problem for a System of Equations of Magnetic Hydrodynamics”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 47, no. 2, Feb. 1995, pp. 168–173, https://umj.imath.kiev.ua/index.php/umj/article/view/5400.