Question: Who developed one of the foundations of functional analysis and also taught Hugo Steinhaus?
Sentence (from "Hugo Steinhaus"): Steinhaus obtained his PhD under David Hilbert at Göttingen University in 1911 and later became a professor at the Jan Kazimierz University in Lwów (now Lviv, Ukraine), where he helped establish what later became known as the Lwów School of Mathematics.
Relevant evidence: Yes