Skrypnik, W. I. “Two-Dimensional Coulomb Dynamics of Two and Three Equal Negative Charges in the field of Two Equal Fixed Positive Charges”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 68, no. 11, Nov. 2016, pp. 1528-39, http://umj.imath.kiev.ua/index.php/umj/article/view/1939.