1. Fundamentals of Mathematics, Volume II, Geometry, H. Behnke. F. Bachman, K. Fladt, and H. Kunle, editors; translated by S. H. Gould, MIT Press, Cambridge, 1974.
2. Peter Pearce, Structure in Nature is a Strategy for Design, MIT Press, Cambridge, 1978.
3. Alan Holden, Shapes, Space and Symmetry, Columbia University Press, New York, 1971.
4. The Probability of Heads