CREATE TABLE table_72663 ("Year" FLOAT, "Dates" TEXT, "Champion" TEXT, "Country" TEXT, "Score" TEXT, "To par" TEXT, "Margin of victory" TEXT, "Purse  (  US$  ) " FLOAT, "Winners share" FLOAT)

What countries have a margin of victory at 6 strokes?
SELECT "Country" FROM table_72663 WHERE "Margin of victory" = '6 strokes'
SELECT "Country" FROM "table_72663" WHERE "Margin of victory" = '6 strokes'