Skorobogatko, V. Y., and E. I. Bobik. “Concerning the Article «Expansion of Linear and Nonlinear Operators into Real Factors”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 18, no. 4, June 1966, p. 138, https://umj.imath.kiev.ua/index.php/umj/article/view/8326.