1. Function Theoretic Methods in Partial Differential Equations;Gilbert,1969
2. Integral Operators in the Theory of Linear Partial Differential Equations;Bergman,1961
3. New Methods for Solving Elliptic Equations;Vekua,1967
4. Zur Funktionentheorie der Wellengleichung;Henrici;Comment. Math. Helv.,1953
5. A survey of I.N. Vekua's theory of elliptic partial differential equations with analytic coefficients;Henrici;Z. Angew. Math. Phys.,1957