@article {ascherio2013vitamin, title = {Vitamin D as a predictor of multiple sclerosis activity and progression.}, year = {2013}, author = {Ascherio, A and Munger, K and White, R and Kochert, K and Simon, C and Polman, C and Freedman, MS and Hartung, HP and Miller, DH and Montalban, X and others} }