1. Sobolev Spaces;Adams,1975
2. Lectures on Elliptic Boundary Value Problems;Agmon,1965
3. The Rayleigh-Ritz and A. Weinstein methods for approximation of eigenvalues, I: Operators in a Hilbert space; II: Differential operators;Aronszajn,1948
4. The Rayleigh-Ritz and A. Weinstein methods for approximation of eigenvalues, I: Operators in a Hilbert space; II: Differential operators;Aronszajn,1948
5. The Rayleigh-Ritz and the Weinstein methods for approximation of eigenvalues;Aronszajn,1949