1. Canonical regular expressions and minimal state graphs for definite events;Brzozowski,1963
2. Roots of star events;Brzozowski;J. ACM,1967
3. On decompositions of regular events;Brzozowski;J. ACM,1969
4. Characterizations of locally testable events;Brzozowski,1971
5. Finite automata and unary languages;Chrobak;Theoret. Comput. Sci.,1986