ZaviyalovО. I. and PolivanovМ. K. (1992) “R-operation of Bogolyubov—Parasyuk and operator expansions in mass-free theories ”, Ukrains’kyi Matematychnyi Zhurnal, 44(3), pp. 333-340. Available at: https://umj.imath.kiev.ua/index.php/umj/article/view/8102 (Accessed: 27July2024).