a little biography of Emil Post. Martin Davis, Computability: with Notes by Barry Jacobs, Courant Institute of Mathematical Sciences, New York University, 1974. Martin Davis, Ron Sigal, Elaine J. Weyuker, (1994) Computability, Complexity, and Languages: Fundamentals of Theoretical Computer Science – 2nd edition, Academic Press: Harcourt, Brace & Company, San Diego, 1994 (First edition, 1983). Fred Hennie, Introduction to Computability, Addison–Wesley, 1977. Marvin Minsky, (1961), Recursive Unsolvability of Post's problem of 'Tag' and other Topics in Theory of Turing Machines, Annals of Mathematics, Vol. 74, No. 3, November, 1961. Roger Penrose, The Emperor's New Mind: Concerning computers, Minds and the Laws of Physics, Oxford University Press, Oxford England, 1990 (with corrections). Cf. Chapter 2, "Algorithms and Turing Machines". An overcomplicated presentation (see Davis's paper for a better model), but a thorough presentation of Turing machines and the halting problem, and Church's lambda calculus. Hao Wang (1957): "A variant to Turing's theory of computing machines", Journal of the Association for Computing Machinery (JACM) 4, 63–92. Turing machine Models of computation