A Characterization of Context-free String Languages by Directed Node-label Controlled Graph Grammars.

Dirk Janssens Grzegorz Rozenberg A Characterization of Context-free String Languages by Directed Node-label Controlled Graph Grammars. 63-85 1981 16 Acta Inf. db/journals/acta/acta16.html#JanssensR81