1. Lecture Notes in Computer Science;D. Hofbauer,1989
2. Lecture Notes in Computer Science;M. Avanzini,2008
3. Simmons, H.: The realm of primitive recursion. ARCH 27, 177–188 (1988)
4. Bellantoni, S., Cook, S.: A new recursion-theoretic characterization of the polytime functions. CC 2, 97–110 (1992)
5. Lecture Notes in Computer Science;N. Hirokawa,2008