In this article we consider the behavior in the vicinity of infinity of the class of all planar quadratic differential systems. This family depends on twelve parameters but due to action of theâ€¦ (More)

In this article we consider the action of affine group and time rescaling on planar quadratic differential systems. We construct a system of representatives of the orbits of systems with at leastâ€¦ (More)

In this article we determine the global geometry of the planar quadratic differential systems with a weak focus of third order. This class plays a significant role in the context of Hilbertâ€™s 16-thâ€¦ (More)

In this article we prove that all real quadratic differential systems dx dt = p(x, y), dy dt = q(x, y) with gcd(p, q) = 1, having invariant lines of total multiplicity at least five and a finite setâ€¦ (More)

Planar quadratic differential systems occur in many areas of applied mathematics. Although more than one thousand papers were written on these systems, a complete understanding of this class is stillâ€¦ (More)

In this article we consider the class QSL4 of all real quadratic differential systems dx dt = p(x, y), dy dt = q(x, y) with gcd(p, q) = 1, having invariant lines of total multiplicity four and aâ€¦ (More)

In this work we consider the problem of classifying all configurations of singularities, both finite and infinite of quadratic differential systems, with respect to the geometric equivalence relationâ€¦ (More)

In this work we consider the problem of classifying all configurations of singularities, both finite and infinite of quadratic differential systems, with respect to the geometric equivalence relationâ€¦ (More)

In the topological classification of phase portraits no distinctions are made between a focus and a node and neither are they made between a strong and a weak focus or between foci of differentâ€¦ (More)

In this article we consider the action of affine group and time rescaling on planar quadratic differential systems. We construct a system of representatives of the orbits of systems with fourâ€¦ (More)