Equations of the mixed type. Translated by P. Zador. Translation edited by I.N. Sneddon. Bit︠s︡adze, A. V. (Andreĭ Vasilʹevich), 1916-1994. Differential equations, Partial. QA377 .B683 1964 517.38 BIE Bibliography: p. 151-156. Oxford, New York : Pergamon Press; [distributed in the Western Hemisphere by Macmillan, New York] 1964. 1964. 1964 Text xiii, 160 p. eng eng rus