1. Turtle geometry;Abelson,1982
2. Compilers: Principles, techniques, and tools;Aho,1986
3. Simulation of organisms using a developmental model, parts I and II;Baker;International Journal of Bio-Medical Computing,1972
4. Parameterized L systems for modelling: Potential and limitations;Chien,1992
5. K. A. Erstad. L-systems, twining plants, Lisp. Master's thesis, University of Bergen, January 2002.