Кофанов, В. О. “The Bojanov-Naidenov Problem for the Functions With Non-Symmetric Restrictions on the Oldest Derivative”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 71, no. 3, Jan. 2021, pp. 368-81, http://umj.imath.kiev.ua/index.php/umj/article/view/254.