1. Random processes and transformations;Ulam;Proc. Intern. Cong. Math.,1950
2. Random processes and transformations;Ulam,1952
3. Theory of Self-Reproducing Automata;von Newmann,1966
4. Universality in the von Neumann cellular model;Thatcher,1964
5. Variants of Thatcher's algorithm for constructing pulsers;Hedetniemi,1964