VlasenkoL. A., Piven’A. L., and RutkasA. G. “Criteria for the Well-Posedness of the Cauchy Problem for Differential Operator Equations of Arbitrary Order”. Ukrains’kyi Matematychnyi Zhurnal 56, no. 11 (November 25, 2004): 1484-1500. Accessed November 24, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/3860.