Kirjackis, Eduardas, and Jevgenijus Kirjackis. “On Some Properties of the Linear-Invariant Family of N-Th Order”. Lietuvos matematikos rinkinys 46, no. spec. (September 21, 2023): 48–52. Accessed May 17, 2024. https://www.journals.vu.lt/LMR/article/view/30571.