The Cartesian product of sets and the Hessenberg natural product of ordinals.
(English).Czechoslovak Mathematical Journal,
vol. 29
(1979),
issue 3,
pp. 353-358
[2] Ehrenfeucht A.: Polynomical functions with exponentiation are well ordered. Algebra Universalis, vol. 3, (1973) pp. 261-262. DOI 10.1007/BF02945125 | MR 0332582