[18]-Annulene, C18H18, structure, disorder and Hückel's 4n + 2 rule Gorter, S. ; Rutten-Keulemans, E. ; Krever, M. ; Romers, C. ; Cruickshank, D. W. J. Abstract Publication: Acta Crystallographica Section B Pub Date: December 1995 DOI: 10.1107/S0108768195004927 Bibcode: 1995AcCrB..51.1036G