RONTO, A. M. Exact Solvability Conditions for the Cauchy Problem for Systems of First-Order Linear Functional-Differential Equations Determined by $(σ_1, σ_2, ... , σ_n; τ)$-Positive Operators. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 55, n. 11, p. 1541–1568, 2003. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/4023. Acesso em: 5 dec. 2025.