1. I.Snook and A.Barnard , Graphene Nano-Flakes and Nano-Dots: Theory, Experiment and Applications , 2011
2. E.Clar , Polycyclic Hydrocarbons , Academic Press , London , 1964 , vol. 2
3. E.Clar , The aromatic sextet , Wiley , London , 1972
4. Forty years of Clar's aromatic π-sextet rule
5. 8-13 micron spectra of NGC 7027, BD +30 3639 and NGC 6572.