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6. Highmark Medicare Services. LCD L27536: transthoracic echocardiography. www.highmarkmedicareservices. com/policy/mac-ab/l27536-r3.html. Updated Septem-ber 23, 2008. Accessed October 16, 2008.
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9. Centers for Medicare and Medicaid Services. Comprehensive error rate testing: overview. www. cms.hhs.gov/CERT/. Updated December 14, 2005. Accessed October 16, 2008.
10. Centers for Medicare and Medicaid Services. Medicare claims processing manual: chapter 12, section 30.6.10G. www.cms.hhs.gov/manuals/downloads/clm104c12.pdf. Updated July 9, 2008. Accessed October 16, 2008.