Cita APA (7th ed.)

FREDRICHS K O. (1965). PERTURBATION OF SPECTRA IN HELBERT SPACE. -.

Cita Chicago (17th ed.)

FREDRICHS K O. PERTURBATION OF SPECTRA IN HELBERT SPACE. -: -, 1965.

Cita MLA (9th ed.)

FREDRICHS K O. PERTURBATION OF SPECTRA IN HELBERT SPACE. -, 1965.