The effect of vitamin D and frailty on mortality among non-institutionalized US older adults. - Smit E; Crespo CJ; Michael Y; Ramirez-Marrero FA; Brodowicz GR; Bartlett S; Andersen RE; Smit, E; Crespo, C J; Michael, Y; Ramirez-Marrero, F A; Brodowicz, G R; et al. (European Journal of Clinical Nutrition, 2012)