matematica TecaLibri A.M. Turing: opere 1937 On computable numbers with an application to the Entscheidungsproblem in: Proc. Lond. Math. Soc. (ser. 2), 42, pp. 230-265 1939 Systems of logic based on ordinals in: P. Lond. Math. Soc., 45, pp. 161-228