1. Working ’round the clock;Trossman;Am Nurse,1999
2. U.S. Department of Commerce, Bureau of the Census: Current Population Survey (www.ferret.bls.census.gov/cgi-bin/ferret), Apr 27, 1999.
3. www.bls.census.gov/cps/pub/empsit_1199; Dec 15, 1999.
4. The health care workforce;Kovner,1999