The Effects of Four Doses of Vitamin D Supplements on Falls in Older Adults : A Response-Adaptive, Randomized Clinical Trial. - Appel LJ; Michos ED; Mitchell CM; Blackford AL; Sternberg AL; Miller ER 3rd; Juraschek SP; Schrack JA; Szanton SL; Charleston J; Minotti M; Baksh SN; et al. (Annals of internal medicine, 2021)