Geodesic
A complete classification of quadratic differential systems according to the dimensions of Aff(2,R)-orbits
Buletinul Academiei de Ştiinţe a Republicii Moldova. Matematica, no. 2 (2009), pp. 29-54.

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In this article we consider the action of the group Aff(2,R) of affine transformations and time rescaling on real planar quadratic differential systems. Via affine invariant conditions we give a complete stratification of this family of systems according to the dimension D of affine orbits proving that 3≤D≤6. Moreover we give a complete topological classification of all the systems located on the orbits of dimension D≤5 constructing the affine invariant criteria for the realization of each of 49 possible topologically distinct phase portraits. 
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N. Gherstega; V. Orlov; N. Vulpe. A complete classification of quadratic differential systems according to the dimensions of $Aff(2,\mathbb R)$-orbits. Buletinul Academiei de Ştiinţe a Republicii Moldova. Matematica, no. 2 (2009), pp. 29-54. https://geodesic-test.mathdoc.fr/item/BASM_2009_2_a2/

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