4,9-Dimethyl-2,3,5,6-dibenzothio-phenthrene ,its CAS number is 63042-50-2,it can be called Benzo(b)phenanthro(3,2-d)thiophene, 7,13-dimethyl- ; 7,13-Dimethylbenzo(b)phenanthro(3,2-d)thiophene .