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Gifford KA, Followill DS, Liu HH, Starkschall G.Gifford KA, et al. Among authors: followill ds.J Appl Clin Med Phys. 2002 Winter;3(1):26-45. doi: 10.1120/jacmp.v3i1.2589.J Appl Clin Med Phys. 2002.PMID: 11818002Free PMC article.