Schema: CREATE TABLE table_18733814_2 (general_classification VARCHAR, points_classification VARCHAR, young_rider_classification VARCHAR)
Question: When thomas löfkvist is the  young rider classification and alessandro petacchi is the points classification who are the general classifications? 
SQL: SELECT general_classification FROM table_18733814_2 WHERE points_classification = "Alessandro Petacchi" AND young_rider_classification = "Thomas Löfkvist"