1. Guo, Y.Q., H.J. Shyr and G. Thierrin,F-disjunctive languages, Intern. J. Computer Math., Vol. 18(1986), p. 219–237.
2. Guo, Y.Q., H.J. Shyr and G. Thierrin,Of-disjunctive Languages, Papers on Automata and Languages, Vol. VII, 1985-1, p. 1–28.
3. Lallement, G.,Semigroups and combinatorial applications, Wiley-Interscience, New York (1979).
4. Long Donyang,An f-disjunctive context-free prefix code, Science Bulletin (China), Vol. 31, No. 12 June 1986, p. 859–860.
5. Guo, Y.Q., G. Thierrin and G.W. Xu,Disjunctive decomposition of languages, Theoretical Computer Science (1986), Vol. 46, p. 47–51.