  A plane graph is called a rectangular graph if each of its edges can be
oriented either horizontally or vertically, each of its interior regions is a
four-sided region and all interior regions can be fitted in a rectangular
enclosure. Only planar graphs can be dualized. If the dual of a plane graph is
a rectangular graph, then the plane graph is a rectangularly dualizable graph.
  In 1985, Ko\'zmi\'nski and Kinnen presented a necessary and sufficient
condition for the existence of a rectangularly dualizable graph for a separable
connected plane graph. In this paper, we present a counter example for which
the conditions given by them for separable connected plane graphs fail and
hence, we derive a necessary and sufficient condition for a plane graph to be a
rectangularly dualizable graph.
