ASPLUND, S. O. Finite Boundary Value Problems Solved by Green’s Matrix. MATHEMATICA SCANDINAVICA, [S. l.], v. 7, p. 49–56, 1959. DOI: 10.7146/math.scand.a-10560. Disponível em: https://www.mscand.dk/article/view/10560. Acesso em: 7 may. 2024.