“…These two interpretations strongly suggest that the desired construction can in general be effected only by an appeal to inductive methods, based on mathematical (or complete) induction in the case of countably infinite Boolean rings and on transfinite induction in the higher cases. [25], and by McCoy and Montgomery [22]. It should be carefully observed, however, that certain of these constructions may be regarded as contained in somewhat earlier results established by Krull, Lindenbaum, Tarski, and Ulam.…”