CREATE TABLE table_76409 ("Outcome" TEXT, "Date" FLOAT, "Championship" TEXT, "Surface" TEXT, "Partner" TEXT, "Opponents in the final" TEXT, "Score in the final" TEXT)

What was the surface in 1981?
SELECT "Surface" FROM table_76409 WHERE "Date" = '1981'
SELECT "Surface" FROM "table_76409" WHERE "Date" = '1981'