1. National Ambulatory Medical Care Survey: 1973 summary, United States, May 1973–April 1974. National Center for Health Statistics;DeLozier;Vital Health Stat,1975
2. National Ambulatory Medical Care Survey: 1989 Summary;DeLozier,1991
3. U. S. Department of Commerce, Bureau of the Census.
4. A reason for visit classification for ambulatory care. National Center for Health Statistics;Schneider;Vital Health Stat,1979
5. International Classification of Diseases,1980