1. Erasable ink; something old, something new
2. Erasable Pens Explanation Page.http://www.ehow.com/how-does_4922720_erasable-pens-work.html(accessed Jan 2012) .
3. Pilot Corporation of America. frixioncity.com: Products. http://www.frixioncity.com/(accessed Jan 2012) . The product precautions are also stated on the pen packaging.
4. Farnham, N. W.; Gosnell, E. J.Colorforming Compositions and Methods for Preparing and Controlling Same. U.S. Patent 3,560,229, Feb. 2, 1971.
5. Nakasuji, N.; Kataoka, T.; Inagaki, H.; Nakashima, S.Thermochromic Materials. U.S. Patent 4,028,118, June 7, 1977.