Prospective epidemiological study on the beginning of varicose veins – Bochum Study I-IV - Schultz-Ehrenburg, U; Reich-Schupke, S; RobakPawelczyk, B; Rudolph, T; Moll, C; Weindorf, N; Hirche, H; Altmeyer, P; Stücker, M (Phlebologie, 2009)