Carmichael RD (1913). "On the impossibility of certain Diophantine equations and systems of equations". Amer. Math. Monthly. 20 (7): 213–221. doi:10.2307/2974106. JSTOR2974106.
Carmichael RD (1913). "On the impossibility of certain Diophantine equations and systems of equations". Amer. Math. Monthly. 20 (7): 213–221. doi:10.2307/2974106. JSTOR2974106.