RT Journal Article SR Electronic T1 The plasma ammonia response to cycle exercise in chronic obstructive pulmonary disease JF European Respiratory Journal JO Eur Respir J FD European Respiratory Society DO 10.1183/09031936.00164106 A1 L.D. Calvert A1 S.J. Singh A1 P.L. Greenhaff A1 M.D. Morgan A1 M.C. Steiner YR 2007 UL http://erj.ersjournals.com/content/early/2007/12/19/09031936.00164106.abstract AB