eng Ansari Education and Research Society Journal of Ultra Scientist of Physical Sciences August 2009 21 2 583 584 jusps-A 1227 article R. Ganapathy Raman 1 R. Sattanathan 2 Department of Maths D.G. Vaishnav College, Chennai & Research Scholar in SCSVMYU (INDIA H.O.D. of Maths D.G. Vaishnav College, Chennai (INDIA) <p style="text-align:justify">Of interest in this theory is the question of determining the circular chromatic number of product graphs. There are four kinds of graph products: (i) Cartesian Product (G  H), (ii) Categorical Product (G &times; H), (iii) Lexicographic Product (G . H) and (iv) Strong product (G H). We discuss some theorems on circular chromatic number of lexicographic products.</p> https://www.ultrascientist.org/paper/1227/ Circular chromatic lexicographic productsu00a0