1. A machine independent theory of the complexity of recursive functions;Blum;J. Assoc. Comput. Mach.,1967
2. On the size of machines;Blum;Inform. and Control,1967
3. On the simplicity of busy beaver sets;Daley;Z. Math. Logik Grundlag. Math.,1978
4. Busy beaver sets and the degrees of unsolvability;Daley;J. Symbolic Logic,1981
5. Retraceability, repleteness, and busy beaver sets;Daley,1981