CREATE TABLE table_51661 ("Edition" TEXT, "Round" TEXT, "Date" TEXT, "Surface" TEXT, "Opponent" TEXT, "Result" TEXT)

What surface was the April 24, 2003 match played on?
SELECT "Surface" FROM table_51661 WHERE "Date" = 'april 24, 2003'
SELECT "Surface" FROM "table_51661" WHERE "Date" = 'april 24, 2003'