Geodesic
A note on the saddle conic of quadratic planar differential systems
Electronic journal of differential equations, Tome 2000 (2000)
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).
Classification : 34C05, 34C20
Keywords: nonlinear differential systems, saddle points, qualitative theory of ordinary differential systems, critical points, invariant theory 
@article{EJDE_2000__2000__a62,
     author = {Boularas,  D.},
     title = {A note on the saddle conic of quadratic planar differential systems},
     journal = {Electronic journal of differential equations},
     year = {2000},
     volume = {2000},
     zbl = {0947.34012},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/EJDE_2000__2000__a62/}
}
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%A Boularas,  D.
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%J Electronic journal of differential equations
%D 2000
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Boularas,  D. A note on the saddle conic of quadratic planar differential systems. Electronic journal of differential equations, Tome 2000 (2000). http://geodesic.mathdoc.fr/item/EJDE_2000__2000__a62/