J. D. Hamkins, “Every group has a terminating transfinite automorphism tower,” Pr~Amer.~Math.~Soc., vol 126, iss 11, pp 3223-3226, 1998.
J. D. Hamkins, “Every group has a terminating transfinite automorphism tower,” Proc.~Amer.~Math.~Soc., vol. 126, iss. 11, pp. 3223-3226, 1998.