Question: What is the date of death of Helen Levitov Sobell's husband?
Sentence (from "Morton Sobell"): Morton Sobell (April 11, 1917 – December 26, 2018) was an American engineer who is known for having been convicted of spying for the Soviet Union when it was an ally of the United States during late World War II; he was charged as part of a conspiracy
Relevant evidence: Yes