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2. A 10-year report of patients in a prolonged respiratory care unit;Indihar;Minn Med,1991
3. Costing nursing care with the Grasp system: costing out nursing: pricing our product;Meyer,1985
4. SAS users’ guide: statistics, version 6, 4th edition: the Lifetest procedure,1990
5. SAS Technical Report P-229: chapter 19: the PHREG procedure,1992