1. Andres R, Hazzard W. Principles of geriatric medicine. New York: McGraw-Hill. 1985: 845
2. Geriatric Medicine
3. Ham RJ. Primary care geriatrics. Boston: Wright-PSG Publishing. 1983: 146
4. Rossman I. Clinical geriatrics. 3d ed Philadelphia: JB Lippincott 1986: 330–1