Ohba has conjectured [7] that if
G has 2
$
\frac{5}
{3}\chi {\left( G \right)} - \frac{4}
{3}.
$
\frac{5}
{3}\chi {\left( G \right)} - \frac{4}
{3}.
Mathematics Subject Classification (2000):
05C15 - 05D40
* This research was partially supported by DIMACS and by CNRS/NSF collaboration grant.
Research supported in part by NSF grants DMS-0106589, CCR-9987845 and by the State of New Jersey.