On Formally Undecidable Propositions of "Principia Mathematica" and Related Systems  (English, Paperback, Godel Kurt)

First English translation of revolutionary paper (1931) that established that even in elementary parts of arithmetic, there are propositions which cannot be proved or disproved within the system. It is thus uncertain that the basic axioms of arithmetic will not give rise to contradictions. Introduction by R. B. Braithwaite.