Minimal coloring number for Z-colorable links
  For a link with zero determinants, a Z-coloring is defined as a generalization of Fox coloring. We call a link having a diagram which admits a non-trivial Z-coloring a Z-colorable link. The minimal coloring number of a Z-colorable link is the minimal number of colors for non-trivial Z-colorings on diagrams of the link. We give sufficient conditions for non-splittable Z-colorable links to have the least minimal coloring number. 
Kazuhiro Ichihara and Eri Matsudo
math.GT