1. P. Berman, A. Lingas, On the complexity of regular languages in terms of finite automata, Techn. Report 304, Polish Academy of Sciences, 1977.
2. Intersection and union of regular languages and state complexity;Birget;Inform. Process. Lett.,1992
3. Partial orders on words, minimal elements of regular languages, and state complexity;Birget;Theoret. Comput. Sci.,1993
4. J.C. Birget, ERRATUM: partial orders on words, minimal elements of regular languages, and state complexity, 2002. Available at: http://clam.rutgers.edu/∼birget/papers.html.
5. State complexity of basic operations on finite languages;Câmpeanu,2001