1. Analytic Structure of Energy Levels in a Field-Theory Model
2. Functional Integration and Quantum Physics (Academic, New York, 1979).
3. Perturbation Theory for Linear Operators (Springer, Berlin, 1966).
4. Perturbation of Spectra in Hilbert Space (Am. Math. Soc., Providence, RI, 1965).
5. and Methods of Modern Mathematical Physics, IV. Analysis of Operators (Academic, New York, 1978).