Question: What nationality is Marta Casals Istomin's husband?
Sentence (from "Marta Casals Istomin"): Marta Casals Istomin (born November 2, 1936), who uses the surnames of her first husband, Pablo Casals, and her second husband, Eugene Istomin, is a musician from Puerto Rico, and the former president of the Manhattan School of Music.
Relevant evidence: Yes