1. Okhotin, A.: Conjunctive grammars. Journal of Automata, Languages and Combinatorics 6(4), 519–535 (2001)
2. Okhotin, A.: An overview of conjunctive grammars. Formal Language Theory Column. Bulletin of the EATCS 79, 145–163 (2003)
3. Okhotin, A.: Boolean grammars. Information and Computation 194(1), 19–48 (2004)
4. Okhotin, A.: Nine open problems on conjunctive and boolean grammars. TUCS Technical Report, p. 794 (2006)