1. Centers for Medicare and Medicaid Services. https://www.cms.gov/AcuteInpatientPPS/02_stepspps.asp#TopOfPage
2. Davis , P. A. J. Hahn P. C. Morgan J. Stone S. Tilson 2010 http://healthreform.kff.org/~/media/Files/KHS/docfinder/CRS%20Report%20on%20Medicare%20Provisions%20in%20PPACA%20and%20Timeline.pdf
3. The Cost-Shift Payment ‘Hydraulic’;Dobson;Health Affairs,2006
4. Foster , RS. 2010 https://www.cms.gov/ActuarialStudies/Downloads/PPACA_2010-04-22.pdf