Breneman, Curt M.; Wiberg, Kenneth B. (1990). “Determining atom-centered monopoles from molecular electrostatic potentials. The need for high sampling density in formamide conformational analysis”. Journal of Computational Chemistry11 (3): 361. doi:10.1002/jcc.540110311.
Singh, U. Chandra; Kollman, Peter A. (1984). “An approach to computing electrostatic charges for molecules.”. Journal of Computational Chemistry5 (2): 129–145. doi:10.1002/jcc.540050204.