Dewar, M. J. S., Haddon, R. C., Li, W.-K., Thiel, W., & Weiner, P. K. (1975). Ground States of Molecules. XXXI. MINDO/3 Study of CH2, NH2+, and O2. Journal of the American Chemical Society, 97(16), 4540-4545. doi:10.1021/ja00849a015.