Primary conceptual reference:
Prusinkiewicz, P., and Lindenmayer, A. The Algorithmic Beauty of Plants. Springer-Verlag, 1990. Chapters 1–8 and Appendix A.
Implementation comments cite relevant chapters/sections without copying prose, figures, photographs, or source listings. The package independently expresses the algorithms in typed, bounded, renderer-neutral form. The book and its illustrations are not distributed or licensed with this project.