Reference

1."Physics for scientists and Engineers with Modern Physics," New Jersey: Pearson Prentice Hall, 2009 by Douglas C. Giancoli

.

2."Elements of Electromagnetics," New York: Oxford University Press, 2006 by Mattew.N.O.Sadiku

3."Engineering Electromagnetics," New Delhi: McGraw Hill, 2006. by William H. Hayt, Jr., John A. Buck.

WEB REFERENCES:

en.wikipedia.org/wiki/Coulomb's_law

http://www.answers.com/topic/coulomb-s-law

http://www.physicsclassroom.com/class/estatics/u8l3b.cfm

http://www.edumedia-sciences.com/en/a120-coulomb-s-law

http://webphysics.davidson.edu/physlet_resources/assessment/coulombs_law/part1a.html