1. E. Artin (1957) Geometric Algebra, Interscience.
2. P. Alexandroff and H. Hopf (1935) Topologie, I., Springer.
3. M.K. Bennett and G. Birkhoff, Algebraic foundations of geometry (unpublished manuscript).
4. H. Crapo and G.-C. Rota, Geometric Lattices, M.I.T. Press, Second ed. in preparation.
5. Branko Grünbaum (1967) Convex Polytopes, Interscience.