  High massive compact stars have been reported recently in the literature,
providing strong constraints on the properties of the ultradense matter beyond
the saturation nuclear density. In view of these results, the calculations of
quark star or hybrid star equilibrium structure must be compatible with the
provided observational data. But, since the used equations of state describing
quark matter are in general too soft, in comparison with the equation of states
used to describe the hadronic or nuclear matter, the calculated quark star
models presented in the literature are in general not suitable to explain the
stability of high compact massive objects.
