CREATE TABLE table_name_76 (stage VARCHAR(255), young_rider_classification VARCHAR(255), intergiro_classification VARCHAR(255), points_classification VARCHAR(255))
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?
    
SQL: SELECT stage FROM table_name_76 WHERE intergiro_classification = "miguel indurain" AND points_classification = "mario cipollini" AND young_rider_classification = "leonardo sierra"