Electronic Journal of Differential Equations,
Vol. 2000(2000), No. 23, pp. 1-9.

Title: A note on the saddle conic of quadratic planar differential systems

Author: D. Boularas (Univ. de Limoges, France)
         
Abstract: 
 We give some properties of the saddle conic of quadratic differential 
 systems. We also deduce semi-algebraic conditions for the existence 
 of one, two or three saddle points (in terms of affine invariants).

Submitted December 16, 1999. Published March 28, 2000.
Math Subject Classifications: 34C05, 34C20.
Key Words: nonlinear differential systems; saddle points; 
     qualitative theory of ordinary differential systems; 
     critical points; invariant theory.