Un lemme combinatoire de H. B. Neumann

Abstract

We give a notably simpler and shorter proof of H. B. Neumann's result which is stated, cursorly, like this. For any well-ordered subset, A, of a totally ordered semigroup, the set of products of any finite number of elements of A is itself well-ordered. Moreover, for each t, there are only a finite number of such products equal to t.