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2. Turtle geometry;Abelson,1986
3. The fracal geometry of nature;Mandelbrot,1982
4. Prusinkiewicz P. Graphical applications of l-systems. Proceedings of graphics interface 86 and vision interface 86; Vancouver, B.C., Canada 1986. p. 247–53.
5. The algorithmic beauty of plants;Prusinkiewicz,1992