CREATE TABLE table_name_56 (tournament VARCHAR(255), margin_of_victory VARCHAR(255), date VARCHAR(255))
What is the name of the tournament played on Sep 20, 1981, ending with a margin of vicroty of 2 strokes?
    
SQL: SELECT tournament FROM table_name_56 WHERE margin_of_victory = "2 strokes" AND date = "sep 20, 1981"