Newman, M. H. A. and Turing, Alan M. (1942) A Formal Theorem in Church's Theory of Types. J. Symb. Log., 7 (1). pp. 28-33.
Turing, Alan M. (1942) The Use of Dots as Brackets in Church's System. J. Symb. Log., 7 (4). pp. 146-156.