no. 4
The rule of induction in the three variable arithmetic based on + and -
Annales de la faculté des sciences de l'université de Clermont. Mathématiques, Tome 35 (1967) no. 4, pp. 25-31. 
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     title = {The rule of induction in the three variable arithmetic based on $+$ and $-$},
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     year = {1967},
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Shepherdson, J. C. The rule of induction in the three variable arithmetic based on $+$ and $-$. Annales de la faculté des sciences de l'université de Clermont. Mathématiques, Tome 35 (1967) no. 4, pp. 25-31. http://www.numdam.org/item/ASCFM_1967__35_4_25_0/

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Shepherdson J.C. [2] - Non Standard models for fragments of number theory, Proc. Int. sympodium on Model Theory, Berkeley 1963. | Zbl

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