“…As we will see in this section, the origin of system (1.1) can be found in the study of the analytic unfoldings of the so called Hopf-zero singularity. More concretely, let us consider a vector field in R 3 which has the origin as a critical point and, for some positive α * , the eigenvalues of the linear part at the origin are 0, ±α The unfoldings of this singularity in the conservative case and all the different behaviour these families can present have been broadly studied [17,19,18,14,5,1,10,7,11,6,15]. The standard way to proceed in the study of these unfoldings, is to use the normal form theory to write the vector field as simple as possible up to some order and then to study the effects of the non symmetric terms in the dynamics.…”