6-minute walk distance in healthy North Africans older than 40 years: influence of parity - Ben Saad, H; Prefaut, C; Tabka, Z; Mtir, A H; Chemit, M; Hassaoune, R; Ben Abid, T; Zara, K; Mercier, G; Zbidi, A; Hayot, M (Respir Med, 2009)