Editing Register machine (section)

== Precedence ==
Minsky was working at the [[MIT Lincoln Laboratory]] and published his work there; his paper was received for publishing in the ''Annals of Mathematics'' on 15 August 1960, but not published until November 1961.<ref name="Minsky_1961"/> While receipt occurred a full year before the work of Melzak<ref name="Melzak_1961"/> and Lambek<ref name="Lambek_1961"/> was received and published (received, respectively, May and 15 June 1961, and published side-by-side September 1961). That (i) both were Canadians and published in the [[Canadian Mathematical Bulletin]], (ii) neither would have had reference to Minsky's work because it was not yet published in a peer-reviewed journal, but (iii) Melzak references Wang, and Lambek references Melzak, leads one to hypothesize that their work occurred simultaneously and independently.

Almost exactly the same thing happened to Shepherdson and Sturgis.<ref name="Shepherdson-Sturgis_1961"/> Their paper was received in December 1961—just a few months after Melzak and Lambek's work was received. Again, they had little (at most 1 month) or no benefit of reviewing the work of Minsky. They were careful to observe in footnotes that papers by Ershov,<ref name="Ershov_1958"/> Kaphengst<ref name="Kaphengst_1959"/> and Péter<ref name="Péter_1958"/> had "recently appeared"<ref name="Shepherdson-Sturgis_1961"/>{{rp|page=219}} These were published much earlier but appeared in the German language in German journals so issues of accessibility present themselves.

The final paper of Shepherdson and Sturgis did not appear in a peer-reviewed journal until 1963.<ref name="Shepherdson-Sturgis_1963"/> And as they note in their Appendix A, the 'systems' of Kaphengst (1959),<ref name="Kaphengst_1959"/> Ershov (1958),<ref name="Ershov_1958"/> and Péter (1958)<ref name="Péter_1958"/> are all so similar to what results were obtained later as to be indistinguishable to a set of the following:
: produce 0 i.e. 0 &rarr; n
: increment a number i.e. n+1 &rarr; n
::"i.e. of performing the operations which generate the natural numbers"<ref name="Shepherdson-Sturgis_1963"/>{{rp|page=246}}
: copy a number i.e. n &rarr; m
: to "change the course of a computation", either comparing two numbers or decrementing until 0

Indeed, Shepherson and Sturgis conclude:
::"''The various minimal systems are very similar''"<ref name="Shepherdson-Sturgis_1963"/>{{rp|page=246}}

By order of ''publishing'' date the work of Kaphengst (1959),<ref name="Kaphengst_1959"/> Ershov (1958),<ref name="Ershov_1958"/> Péter (1958) were first.<ref name="Péter_1958"/>