1. Current estimates from the National Health Interview Survey, 1995;Benson;Vital Health Stat 10,1998
2. National Ambulatory Medical Care Survey: 2001 summary;Cherry;Adv Data,2003
3. National Ambulatory Medical Care Survey: 2000 summary;Cherry;Adv Data,2002
4. National Ambulatory Medical Care Survey: 1989 summary;Schappert;Vital Health Stat 13,1992
5. National Ambulatory Medical Care Survey: 1990 summary;Schappert;Adv Data,1992