Theory of linear operators in Hilbert space 2026-02-15T17:38:31+03:00 DEBUG: VuFind\ILS\Driver\Folio: Token taken from global cache: eyJhbGciOiJIUzI1NiJ9.eyJzdWIiO... - Akhiezer, N. I. (Naum Ilich), 1901; Glazman, I. M. (Dover Publications, 1993)