1,1a,3,3a,4,5,5,5a,5b,6-Decachlorooctahydro-1,3,4-metheno-2H-cyclobuta(cd)pentalen-2-one 1,2,3,4,5,5,6,7,8,9,10,10-Dodecachlorooctahydro-1,3,4-metheno-2-cyclobuta(c,d)pentalone 1,2,3,5,6,7,8,9,10,10-Decachloro(5.2.1.0(sup 2,6).0(sup 3,9).0(sup 5,8))decano-4-one 1,3,4-Metheno-2H-cyclobuta(cd)pentalen-2-one, 1,1a,3,3a,4,5,5,5a,5b,6-decachlorooctahydro-