1. American Dental Association Committee on Research in Dental Caries, Dental Caries, 2nd ed. (New York, Lancaster Press: 1941), p. 9.
2. Brekhus, P.J., Your Teeth; Their Past, Present, and Probable Future ( Minneapolis, Univ. of Minn. Press: 1941), pp. 4, 77.
3. Bunting, R.W., AND Hill, T.J., Oral Pathology, 2nd ed. rev. ( Philadelphia, Lea and Febiger: 1940 ), p. 159.
4. Macnevin, M.G., AND Vaughan, H.S., Mouth Infections and Their Relation to Systemic Disease ( New York, Purcell Memorial: 1930 ), p. 372.
5. Merritt, A.H., Periodontal Diseases, 2nd ed. ( New York, MacMillan: 1939), p. 1.