KalmushevskуI. I. “On a Class of Mutually Not Equivalent Volterra Operators”. Ukrains’kyi Matematychnyi Zhurnal 18, no. 3 (April 27, 1966): 116-119. Accessed November 24, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/8745.