TY  - BOOK
AU  - Rellich, Franz
AU  - Berkowitz, J.
TI  - Perturbation theory of eigenvalue problems
T2  - Notes on Mathematics and its applications
SN  - 0677006853
U1  - 515.72 
PY  - 1969///
CY  - New York
PB  - Gordon & Breach Science Publishers Ltd.
ER  -