CREATE TABLE table_71681 ("Date" CLOB, "Tournament" CLOB, "Surface" CLOB, "Opponent in the final" CLOB, "Score" CLOB)

What is the surface at the tournament of Vaihingen?
SELECT "Surface" FROM table_71681 WHERE "Tournament" = 'vaihingen'
SELECT "Surface" FROM "table_71681" WHERE "Tournament" = 'vaihingen'