EBANKS, B. R. On some functional equations of Jessen, Karpf, and Thorup. MATHEMATICA SCANDINAVICA, [S. l.], v. 44, p. 231–234, 1979. DOI: 10.7146/math.scand.a-11807. Disponível em: https://www.mscand.dk/article/view/11807. Acesso em: 2 may. 2024.