1. The Theory of Sound;Strutt,1937
2. Perturbation Theory for Linear Operators;Kato,1966
3. Perturbation Theory of Eigenvalue Problems;Rellich,1969
4. Singular perturbations of eigenvalues;Greenlee;Arch. Rational Mech. Anal.,1969
5. Coupling constant analyticity for the anharmonic oscillator;Simon;Ann. Physics,1970