The reliability and validity of the 4 metre gait speed (4MGS) in idiopathic pulmonary fibrosis (IPF) - Nolan,CM; Maddocks,M; Canavan,JL; Jones,SE; Kon,SSC; Wells,AU; Hansell,DM; Jacobs,J; Cullinan,P; Maher,TM; Man,WD-C (EUROPEAN RESPIRATORY SOC JOURNALS LTD, 2016)