  Chiral Lagrangian and quark-meson coupling models of hyperon matter are used
to estimate the maximum mass of neutron stars. Our relativistic calculations
include, for the first time, both Hartree and Fock contributions in a
consistent manner. Being related to the underlying quark structure of baryons,
these models are considered to be good candidates for describing the dense core
of neutron stars. Taking account of the known experimental constraints at
saturation density, the equations of state deduced from these relativistic
approaches cannot sustain a neutron star with a mass larger than 1.6-1.66
$M_\odot$.
