POGORZELSKI, H. A. Recursive Arithmetic of Skolem II. MATHEMATICA SCANDINAVICA, [S. l.], v. 11, p. 156–160, 1962. DOI: 10.7146/math.scand.a-10662. Disponível em: https://www.mscand.dk/article/view/10662. Acesso em: 6 may. 2024.