1. A. A. Agrachev and R. V. Gamkrelidze, ?Calculation of the Euler characteristic of intersections of real quadrics,? Dokl. Akad. Nauk SSSR,299, No. 1, 11?14 (1988).
2. R. Rockafellar, Convex Analysis, Princeton University Press, Princeton, N.J. (1970).
3. R. Thom and H. I. Levine. ?Singularities of differentiable maps,? in: Singularities of Differentiable Maps [in Russian], Mir, Moscow (1968), pp. 9?101.
4. A. N. Tyurin, ?On intersection of quadrics,? Usp. Mat. Nauk,30, No. 6, 51?100 (1975).
5. M. W. Hirsch, Differential Topology, Springer, New York (1976).