CREATE TABLE table_16751 ("Race Name" TEXT, "Circuit" TEXT, "Date" TEXT, "Winning driver" TEXT, "Constructor" TEXT, "Report" TEXT)

What circuit did Clay Regazzoni win?
SELECT "Circuit" FROM table_16751 WHERE "Winning driver" = 'Clay Regazzoni'
SELECT "Circuit" FROM "table_16751" WHERE "Winning driver" = 'Clay Regazzoni'