1. Theory of Codes;Berstel,1985
2. Languages defined by some partial orders;Day;Soochow J. Math.,1983
3. E-convex infix codes;Guo;Order,1986
4. Semaphore codes and ideals;Guo;J. Inform. Optim. Sci.,1988
5. Introduction to Automata Theory, Languages, and Computation;Hopcroft,1979