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Engelman KK, Cupertino AP, Daley CM, Long T, Cully A, Mayo MS, Ellerbeck EF, Geana MV, Greiner A.Engelman KK, et al.BMC Public Health. 2011 Jan 21;11:47. doi: 10.1186/1471-2458-11-47.BMC Public Health. 2011.PMID: 21255424Free PMC article.Clinical Trial.
Yeh HW, Ellerbeck EF, Mahnken JD.Yeh HW, et al.BMC Med Res Methodol. 2012 Jul 7;12:95. doi: 10.1186/1471-2288-12-95.BMC Med Res Methodol. 2012.PMID: 22770436Free PMC article.Clinical Trial.