SELMER, E. S.; RÖDNE, A. On the postage stamp problem with three stamp denominations, II. MATHEMATICA SCANDINAVICA, [S. l.], v. 53, p. 145–156, 1983. DOI: 10.7146/math.scand.a-12022. Disponível em: https://www.mscand.dk/article/view/12022. Acesso em: 6 may. 2024.