SafaryanR. G. “Two Theorems on Closeness of the Set of Laplace-Type Transformations”. Ukrains’kyi Matematychnyi Zhurnal 45, no. 4 (April 25, 1993): 582–584. Accessed July 27, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/5846.