1. Importance of the problem;Bonica,1987
2. The 50 most frequent diagnosis-related groups, diagnoses, and procedures: statics by hospital size and location;Lemrow,1990
3. Disability; it's more expensive than you think;Chelius;Business Health,1992
4. United States Department of Commerce statistical abstract,1993
5. Experience in the management of patients medically addicted to narcotics;Rayport;JAMA,1954