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Johnson AJ, Ying J, El Gammal T, Timmerman RD, Kim RY, Littenberg B.Johnson AJ, et al. Among authors: ying j.AJNR Am J Neuroradiol. 2007 Jan;28(1):32-7.AJNR Am J Neuroradiol. 2007.PMID: 17213420Free PMC article.