1. V. Arnol’d, A. Varchenko, and S. Gusein-zade, Singularities of Differentiable Mappings [in Russian], Vols. 1, 2, Nauka, Moscow (1982, 1984).
2. L. Blum, F. Cucker, M. Shub, and S. Smale, Complexity and Real Computation, Springer-Verlag (1997).
3. J. Bochnak, J. Cost, and M.-F. Roy, Géométrie Algébrique Réelle, Ergeb. Math., 12, Springer-Verlag (1987).
4. J. Bruce, “Euler characteristics of real varieties,” Bull. Lond. Math. Soc., 22, 213–219 (1990).
5. I. L. Cantor and A. S. Solodovnikov, Hypercomplex Numbers [in Russian], Moscow (1973).