Gerasimenko, V. I., and V. O. Shtyk. “Initial-Value Problem for the Bogolyubov Hierarchy for Quantum Systems of Particles”. Ukrains’kyi Matematychnyi Zhurnal, vol. 58, no. 9, Sept. 2006, pp. 1175–1191, https://umj.imath.kiev.ua/index.php/umj/article/view/3521.