CREATE TABLE table_39355 ("Outcome" TEXT, "Year" FLOAT, "Championship" TEXT, "Surface" TEXT, "Partner" TEXT, "Opponents in the final" TEXT, "Score in the final" TEXT)

Who was the partner when the championship was us open on a hard surface?
SELECT "Partner" FROM table_39355 WHERE "Surface" = 'hard' AND "Championship" = 'us open'
SELECT "Partner" FROM "table_39355" WHERE "Championship" = 'us open' AND "Surface" = 'hard'