[['state (class)', 'vacator', 'reason for change', 'successor', "date of successor 's formal installation"], ['georgia (2)', 'richard russell , jr (d)', 'died january 21 , 1971', 'david h gambrell (d)', 'february 1 , 1971'], ['vermont (1)', 'winston l prouty (r)', 'died september 10 , 1971', 'robert stafford (r)', 'september 16 , 1971'], ['louisiana (2)', 'allen j ellender (d)', 'died july 27 , 1972', 'elaine s edwards (d)', 'august 1 , 1972'], ['georgia (2)', 'david h gambrell (d)', 'successor elected november 7 , 1972', 'sam nunn (d)', 'november 7 , 1972'], ['louisiana (2)', 'elaine s edwards (d)', 'successor elected november 13 , 1972', 'bennett johnston , jr (d)', 'november 14 , 1972']]
2 of the Successor 's Formal Installation took place in November
2 of the [ENT] took place in [ENT]