  Smooth planar vector fields containing two hyperbolic saddles may possess
contours formed by heteroclinic connections between these saddles. We present
an overview of the bifurcations of these contours based on papers by J.W. Reyn
and A.V. Dukov. Additionally, two new explicit polynomial systems containing
such contours are derived, which are studied using the bifurcation software
MatCont and are shown to exhibit the theoretically predicted phenomena,
including series of heteroclinic connections.
