1. National Center for Health Statistics. International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM), 2009. Retrieved September 22, 2009, from http://www.cdc.gov/nchs/icd.htm.
2. Institute of Medicine. Initial national priorities for comparative effectiveness research. Washington, DC: Institute of Medicine, 2009.
3. Centers for Medicare and Medicaid Services. Reporting Hospital Quality Data for Annual Payment Update. Retrieved April 2, 2009, from http://www.cms.hhs.gov/HospitalQualityInits.
4. Accuracy of Administrative Data for Identifying Patients With Pneumonia
5. The accuracy of Medicare's hospital claims data: progress has been made, but problems remain.