Longuet-Higgins, H. C. (1950). "Some Studies in Molecular Orbital Theory I. Resonance Structures and Molecular Orbitals in Unsaturated Hydrocarbons". The Journal of Chemical Physics. 18 (3): 265–274. Bibcode:1950JChPh..18..265L. doi:10.1063/1.1747618.
Longuet-Higgins, H. C. (1950). "Some Studies in Molecular Orbital Theory I. Resonance Structures and Molecular Orbitals in Unsaturated Hydrocarbons". The Journal of Chemical Physics. 18 (3): 265–274. Bibcode:1950JChPh..18..265L. doi:10.1063/1.1747618.