1. A. Arora, C. Lund, R. Motwani, M. Sudan, and M. Szegedy, Proof verification and hardness of approximation problems,Proc. 33rd IEEE Symp. on the Foundation of Computer Science, 1992, pp. 14–23.
2. G. M. Landau and U. Vishkin, Fast parallel and serial approximate string matching,J. Algorithms,10 (1989), 157–169.
3. P. Kilpelainen and H. Mannila, The tree inclusion problem,Proc. Internat. Joint Conf. on the Theory and Practice of Software Development (CAAP '91), 1991, Vol. 1, pp. 202–214.
4. S. Masuyama, Y. Takahashi, T. Okuyama, and S. Sasaki, On the largest common subgraph problem,Algorithms and Computing Theory, RIMS, Kokyuroku (Kyoto University), 1990, pp. 195–201.
5. P. H. Sellers, The theory and computation of evolutionary distances,J. Algorithms,1 (1980), 359–373.