GerasimenkoV. I., and RyabukhaT. V. “Cumulant Representation of Solutions of the BBGKY Hierarchy of Equations”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 54, no. 10, Oct. 2002, pp. 1313-28, https://umj.imath.kiev.ua/index.php/umj/article/view/4170.