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Carpenter G.I, Ikegami N., Ljunggren G., Carrillo E., Fries B.E.  1997.  RUG-III and resource allocation: comparing the relationship of direct care time with patient characteristics in five countries. Age & Ageing. 26(Suppl 2):61-5.

Clauser S.B, Fries B.E.  1992.  Nursing home resident assessment and case-mix classification: cross-national perspectives. Health Care Financing Review. 13(4):135-55.

Cooney, Jr. L.M, Fries B.E.  1985.  Validation and use of resource utilization groups as a case-mix measure for long-term care. Medical Care. 23(2):123-32.

Fries B.E, Cooney, Jr. L.M.  1985.  Resource utilization groups. A patient classification system for long-term care. Medical Care. 23(2):110-22.

Fries B.E, Schneider D.P, Foley W.J, Gavazzi M., Burke R., Cornelius E..  1994.  Refining a case-mix measure for nursing homes: Resource Utilization Groups (RUG-III). Medical Care. 32(7):668-85.