1. An unsolvable problem of elementary number theory;Church;her. jour. of math.,1936
2. Computable functionals of finite type I. Sets, models and recursion theory;Gandy,1967
3. Über formal unentscheidbare Sätze der Principia Mathematica und vewandter Systeme I;Gödel;Monatsh. für Math. und Physik,1931
4. General recursive functions of natural rumbers;Kleene;Math. Ann.,1936
5. A note on recursive functions;Kleene;Bull. her. Math. Soc.,1936