Bicolored digraph grammar systems
ESAIM: Mathematical Modelling and Numerical Analysis - Modélisation Mathématique et Analyse Numérique, Volume 7 (1973) no. R1, p. 45-52
@article{M2AN_1973__7_1_45_0,
     author = {Wood, Derick},
     title = {Bicolored digraph grammar systems},
     journal = {ESAIM: Mathematical Modelling and Numerical Analysis - Mod\'elisation Math\'ematique et Analyse Num\'erique},
     publisher = {Dunod},
     volume = {7},
     number = {R1},
     year = {1973},
     pages = {45-52},
     zbl = {0262.68014},
     mrnumber = {388874},
     language = {en},
     url = {http://www.numdam.org/item/M2AN_1973__7_1_45_0}
}
Wood, Derick. Bicolored digraph grammar systems. ESAIM: Mathematical Modelling and Numerical Analysis - Modélisation Mathématique et Analyse Numérique, Volume 7 (1973) no. R1, pp. 45-52. http://www.numdam.org/item/M2AN_1973__7_1_45_0/

Homsky N., On certainformai properties of grammars, IC 2, 1959, 2, pp. 137-167. | MR 105365

Harary F., Norman R. Z., and Cartwright D., Structural models, 1965, JohnWiley andSon. | Zbl 0139.41503

Rosenkrantz D. J., Programmed grammars and classes offormal languages, JACM 16 1969, 1, pp. 107-131. | MR 235940 | Zbl 0182.02004

Salomaa A., Formal languages, to be published by Academic Press, 1973. | MR 438755 | Zbl 0262.68025