Zholtkevich, G. N., B. V. Novikov, and L. Y. Polyakova. “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.