1. Russell, S. and Norvig, P. (2009) Artificial Intelligence: A Modern Approach, 3rd Edition, Prentice Hall.
2. Feferman, S. Turing’s Thesis http://math.stanford.edu/~feferman/papers/turing.pdf .
3. Zenil, H. (2012)A Computable Universe: Understanding and Exploring Nature as Computation, World Scientific.
4. Letter from Frankel to Brian Randell, 1972 (first published in Randell (1972) ‘On Alan Turing and the origins of digital computers’ in B. Meltzer and D. Michie (eds) Machine Intelligence 7. Edinburgh Press).
5. Alan Turing - BBC Horizon Documentary https://youtu.be/mdz88-fSAjM?t=7m43s and for about 15 mins.