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2. Peyion, F.A., Anthony, D.H., Asger, K., Char-Beneau, G.T., Craig, R.G., and Myers, G.E. Restorative Dental Materials. St. Louis, C. V. Mosby Co., 1960, p. 378.
3. Simon, W.S. Clinical Operative Dentistry. Philadelphia, W. B. Saunders Co., 1956, p. 62.