Independent association between 1,25-dihydroxyvitamin D, 25-hydroxyvitamin D and the renin-angiotensin system: The Ludwigshafen Risk and Cardiovascular Health (LURIC) study - Tomaschitz, A; Pilz, S; Ritz, E; Grammer, T; Drechsler, C; Boehm, B O; Maerz, W (Clin Chim Acta, 2010)