A randomized clinical trial to assess the influence of a three months training program (gym-based individualized vs. calisthenics-based non-individualized) in COPD patients - Greulich, T; Kehr, K; Nell, C; Koepke, J; Haid, D; Koehler, U; Koehler, K; Filipovic, S; Kenn, K; Vogelmeier, C; Koczulla, A R (Respir Res, 2014)