Eric D. Glendening J. K. Badenhoop Frank Weinhold Natural resonance theory: III. Chemical applications. 628-646 1998 19 Journal of Computational Chemistry 6 http://dx.doi.org/10.1002/(SICI)1096-987X(19980430)19:6<628::AID-JCC5>3.0.CO;2-T db/journals/jcc/jcc19.html#GlendeningBW98