A Fractal which can be written as a Lindenmayer System with initial string `"YF"`,
String Rewriting rules `"X" -> "YF+XF+Y", "Y" -> "XF-YF-X"`, and angle 60°.

**References**

Dickau, R. M. ``Two-Dimensional L-Systems.'' http://forum.swarthmore.edu/advanced/robertd/lsys2d.html.

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1999-05-26