Gödel, Kurt, ‘Formally undecidable propositions’: ‘On formally undecidable propositions of Principia mathematica and related systems, I’, From Frege to Gödel: A Source Book in Mathematical Knowledge, 1879–1931, translated by Stefan Bauer-Mengelberg, reprint, Source books in the history of the sciences, Harvard University Press, 1967, pp 596–617.
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