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Blood EA, Cabral H, Heeren T, Cheng DM.Blood EA, et al.BMC Med Res Methodol. 2010 Feb 19;10:16. doi: 10.1186/1471-2288-10-16.BMC Med Res Methodol. 2010.PMID: 20170503Free PMC article.
Blood EA, Cheng DM.Blood EA, et al.BMC Med Res Methodol. 2012 Jan 24;12:5. doi: 10.1186/1471-2288-12-5.BMC Med Res Methodol. 2012.PMID: 22273051Free PMC article.