ZholtkevichG. N., NovikovB. V., and PolyakovaL. Y. “Decomposition of Directed Graphs and the Turán Problem”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 66, no. 7, July 2014, pp. 958–969, https://umj.imath.kiev.ua/index.php/umj/article/view/2191.