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[3] W. V. Quine, New Foundations for Mathematical Logic, American Mathematical Monthly, 44 (1937) 70-80.
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[6] T. Jech, Some Results on Combinators in the System TRC (http://www.math.psu.edu/jech/preprints/combin.ps)
[7] R. Smullyan, To Mock a Mockingbird, A. Knopf, New York, 1985
[8] Hart, J. & Kunen, K. Single Axioms for Odd Exponent Groups, Journal of Automated Reasoning 14 (1995) 383--412 (http://www.cs.wisc.edu/~kunen/odd.ps)