Introduction to the spectral theory of operators in spaces with an indefinite metric / by I.S. Iohvidov, M.G. Krein, H. Langer. (Mathematical research = Mathematische forschung ; Bd. 9)
Introduction to the spectral theory of operators in spaces with an indefinite metric / by I.S. Iohvidov, M.G. Krein, H. Langer.
(Mathematical research = Mathematische forschung ; Bd. 9)