Conversation so far:
when did the milwaukee bucks win the nba championship
The Milwaukee Bucks won an NBA Championship in 1971.
Who was the Milwaukee Bucks' coach in 1971
The Milwaukee Bucks won its only NBA championship in the 1971 NBA Finals under the leadership of its first coach, Larry Costello
When did Larry Costello resign as coach for the Milwaukee Bucks
Larry Costello resigned as coach for the Milwaukee Bucks on November 22, 1976

Question: What year did the coach retire
Self-contained rewrite: What year did coach Larry Costello retire