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Appel K. and W. Haken, Every Planar Map is Four Colorable, Bulletin of American Mathematical society, 82 (1977), 711-712.
Appel K. and W. Haken, Every Planar Map is Four Colorable, Contemporary Mathematics 98, American Mathematical society, (1989).
Brooks R.L., On Coloring of Nodes of a Network, Proc. Cambridge Phil. Society, Vol. 37, 1941, 194-197.
H. R. Bhapkar and J. N. Salunke, *isomorphism of graphs, in International Journal of Mathematical Sciences and Engineering Applications, Vol. 8, No. II, 0973-9424, March 14.
H. R. Bhapkar and J. N. Salunke, The Geometric Dual of HB Graph, *outerplanar Graph and Related Aspects, in Bulletin of Mathematical Sciences and Applications, ISSN 2278-9634, Volume 3, No. 3, pp.114-119, August (2014).
Harary, F. Graph Theory. Reading, MA: Addison-Wesley, pp.113-115, (1994).
Narsingh Deo, Graph Theory with Applications To Engineering and Computer Science, Prentice -Hall of India, 2003, 88-111.
Robin J. Wilson, Introduction to Graph Theory, Pearson, 978-81-317-0698-5, (2011).
Tait P.G., On the coloring of maps, Proceeding Royal Society, Edinburgh Sect. A 10 (18781810), 501-503, 729.
V. K. Balakrishnan, Schaum's outline of theory and problems of graph theory, 198-243, (2008).