Departament de Matem` atiques,

Universitat Aut` onoma de Barcelona,

08193 Bellaterra, Barcelona,

Catalonia, Spain

E-mail:

Universitat Aut` onoma de Barcelona,

08193 Bellaterra, Barcelona,

Catalonia, Spain

E-mail:

**Limit cycles in continuous and discontinuous piecewise linear differential systems with two pieces separated by a straight line**- The problem of the center for cubic differential systems with the line at infinity and an affine real invariant straight line of total algebraic multiplicity five
- The topological classification of a family of quadratic differential systems in terms of affine invariant polynomials
- Levitan Almost Periodic Solutions of Infinite-dimensional Linear Differential Equations
- The classification of a family of cubic differential systems in terms of configurations of invariant lines of the type (3,3)
- On the upper bound of the number of functionally independent focal quantities of the Lyapunov differential system
- On limit cycles of polynomial systems of the first-order ODEs
- Sufficient GL(2,R)-invariant center conditions for some classes of two-dimensional cubic differential systems.
- Invariant conditions of stability of unperturbed motion governed by critical differential systems s(1,2,3)
- Working with professor Nicolae Vulpe