1. Reachability is harder for directed than for undirected finite graphs;Ajtai;Journal of Symbolic Logic,1990
2. A complete logic for reasoning about programs via non-standard model theory, parts I and II;Andréka;Theoretical Computer Science,1982
3. A complete logic for reasoning about programs via non-standard model theory, parts I and II;Andréka;Theoretical Computer Science,1982
4. On the independence of P versus NP;Ben-David;Technical report, Technion-Israel Institute of Technology, Haifa, Israel,1991
5. Model-Theoretic Logics,1985