1. Harvey, E.W.: Modern College Physics, New York: Van Norstand Co., 1948, pp 206-207.
2. Peyton, F.A.; Ascar, K.; Charbeneau, G.T.; Craig, R.G.; and Myers, G.E.: Restoraitve Dental Materials, 3rd ed, St. Louis: C. V. Mosby Co., 1968 , pp 168-181, 199-211.
3. Phillips, R.W., and Skinner, E.W.: Elements of Dental Materials, Philadelphia: W. B. Saunders Co., 1965, pp 61-70.