KHOLKIN, A. THE FUNDAMENTAL SOLUTIONS OF DIFFERENTIAL OPERATOR WITH BLOCK - TRIANGULAR OPERATOR COEFFICIENTS. JOURNAL OF ADVANCES IN MATHEMATICS, [S. l.], v. 10, n. 6, p. 3556–3561, 2015. DOI: 10.24297/jam.v10i6.1720. Disponível em: https://www.rajpub.com/index.php/jam/article/view/1720. Acesso em: 4 jul. 2025.