1. On the structure of polynomial time degrees;Ambos-Spies,1984
2. Sublattices of the polynomial time degrees;Ambos-Spies;Inform. and Control,1985
3. An inhomogeneity in the structure of Karp degrees;Ambos-Spies;SIAM J. Comput,1986
4. Inhomogeneities in the polynomial time degrees: the degrees of super sparse sets;Ambos-Spies;Inform. Process. Lett,1986