1. Constructible Sets in Real Geometry;Andradas,1996
2. M. El Bachraoui, Relation algebras, multigroupoids, and degree, Ph.D. Thesis, University of Amsterdam, 2002.
3. Géométrie Algébrique Réelle;Bochnak,1987
4. Special groups: Boolean-theoretic methods in the theory of quadratic forms;Dickmann;Mem. Amer. Math. Soc.,2000
5. Real semigroups and abstract real spectra I;Dickmann;Cont. Math.,2004