Kollmar, Herbert Max Planck Institute for Medical Research, Max Planck Society;
http://www.sciencedirect.com/science/article/pii/0009261471800854/pdf?md5=da91fb6bc2c8dd1160048cd76ac062ff&pid=1-s2.0-0009261471800854-main.pdf (Any fulltext)
https://doi.org/10.1016/0009-2614(71)80085-4 (Any fulltext)
Kollmar, H. (1971). Semi-empirical MO calculations of hydrocarbon radicals with the half electron method. Chemical Physics Letters, 8(6), 533-536. doi:10.1016/0009-2614(71)80085-4.