1. New Methods for Solving Elliptic Equations, North-Holland, Amsterdam 1967.
2. Integral Operators in the Theory of Linear Partial Differential Equations, Springer, Berlin, 1961.
3. ‘A survey of I. N. Vekua's theory of elliptic partial differential equations with analytic coefficients’, Z. Angew. Math. Phys., 1957.
4. Boundary Methods: An Algebraic Theory, Pitman, Boston, 1984.
5. ‘On generalized finite element methods’, Ph.D. Thesis, University of Maryland, 1995.