user: Question: What is the name of the tournament played on Sep 20, 1981, ending with a margin of vicroty of 2 strokes?
Columns: ['Date', 'Tournament', 'Winning score', 'Margin of victory', 'Runner(s)-up']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['Feb 11, 1968', 'Andy Williams-San Diego Open Invitational', '–15 (66-68-71-68=273)', '1 stroke', 'Al Geiberger']
SQL:

assistant: SELECT "Tournament" FROM "Table" WHERE "Margin of victory" = '2 strokes' AND "Date" = 'Sep 20, 1981';