Khadzhiivanov, N., and N. Nenov. “LETTER TO THE EDITOR. TURAN’S THEOREM AND MAXIMAL DEGREES”. Ann. Sofia Univ. Fac. Math. And Inf., vol. 96, Dec. 2004, pp. 173-4, https://ftl5.uni-sofia.bg./index.php/fmi/article/view/171.