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

Question: When did the coach resign
Self-contained rewrite: When did Larry Costello resign as coach for the Milwaukee Bucks