CREATE TABLE table_name_76 (stage VARCHAR, young_rider_classification VARCHAR, intergiro_classification VARCHAR, points_classification VARCHAR)
During which stage was the Intergiro classification held by Miguel Indurain, the Points classification held by Mario Cipollini, and the Young rider classification held by Leonardo Sierra?
SELECT stage FROM table_name_76 WHERE intergiro_classification = "miguel indurain" AND points_classification = "mario cipollini" AND young_rider_classification = "leonardo sierra"