Sonveaux, E., Andre, J.-M., Delhalle, J., & Fripiat, J. G. (1985). Theoretical-study of the Electronic-structure of Ketene, Ketenimine, Keteniminium Ion and Related Cumulenes - Evaluation of a 1,2-dipolar Model. Societes Chimiques Belges. Bulletin, 94(11-12), 831-847. https://doi.org/10.1002/bscb.19850941111 (Original work published 1985)