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Engelberger RP, Blazek C, Amsler F, Keo HH, Baumann F, Blättler W, Baumgartner I, Willenberg T.Engelberger RP, et al. Among authors: blattler w.BMC Med Res Methodol. 2011 Oct 5;11:138. doi: 10.1186/1471-2288-11-138.BMC Med Res Methodol. 2011.PMID: 21974893Free PMC article.