1. Three small universal Turing machines;Baiocchi,2001
2. John Cocke, Marvin Minsky, Universality of tag systems with p=2, Artificial Intelligence Project–RLE and MIT Computation Center, memo 52, 1963
3. John H. Conway, Unpredictable iterations, in: Proceedings of the 1972 Number Theory Conference, 1972, pp. 49–52
4. Fractran — a simple universal computing language for arithmetic;Conway,1987
5. Universality in elementary cellular automata;Cook;Complex Systems,2004