Means of Hilbert space operators 2026-02-16T04:19:06+03:00 DEBUG: VuFind\ILS\Driver\Folio: Token taken from global cache: eyJhbGciOiJIUzI1NiJ9.eyJzdWIiO... - Hiai, Fumio, 1948-; Kosaki, Hideki (Lecture notes in mathematics,, 2003)