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Ayala A, Rodríguez-Blázquez C, Frades-Payo B, Forjaz MJ, Martínez-Martín P, Fernández-Mayoralas G, Rojo-Pérez F; Grupo Español de Investigación en Calidad de Vida y Envejecimiento.Ayala A, et al.Gac Sanit. 2012 Jul-Aug;26(4):317-24. doi: 10.1016/j.gaceta.2011.08.009. Epub 2012 Jan 21.Gac Sanit. 2012.PMID: 22265651Free article.Spanish.