1. V. M. Alexandrov and E. V. Kovalenko,Problems with Mixed Boundary Conditions in Continuum Mechanics, Nauka, Moscow, 1986. (Russian)
2. Y. W. Chen,Entire solutions of a class of differential equations of mixed type, Comm. Pure Appl. Math.14 (1961), 229–255.
3. M. G. Cowling,On the Littlewood-Paley-Stein theory, Rend. Circ. Mat. Palerno29 (1981), no 1, 21–55.
4. A. Erdelyi (ed.),Higher Transcendental Functions, Vol. I, II, McGraw-Hill, New York, 1953.
5. G. I. Eskin,Boundary Value Problems for Elliptic Pseudodifferential Equations, Amer. Math. Soc., Providence, R.I., 1981.