1. Anthony, L. P. (Ed.), American Textbook of Prosthetic Dentistry, 7th Ed. ( Phila., Lea & Febiger: 1942), p. 212.
2. Prothero, J.H., Prosthetic Dentistry, 3rd Ed. ( Chicago, Medico-Dental: 1923), p. 319.
3. Swenson, M.G., Complete Dentures (St. Louis, Mosby : 1940), p. 399.
4. Schlosser, R. 0., Complete Denture Prosthesis (Phila., Saunders: 1939), p. 49.