RYAN, W. J. Proof of the quadratic reciprocity law in primitive recursive arithmetic. MATHEMATICA SCANDINAVICA, [S. l.], v. 45, p. 177–197, 1979. DOI: 10.7146/math.scand.a-11835. Disponível em: https://tidsskrift.dk/math/article/view/11835. Acesso em: 14 aug. 2026.