Mentz RJ, Schulte PJ, Fleg JL, Fiuzat M, Kraus WE, Piña IL, Keteyian SJ, Kitzman DW, Whellan DJ, Ellis SJ, O'Connor CM. Clinical characteristics, response to exercise training, and outcomes in patients with heart failure and chronic obstructive pulmonary disease: findings from Heart Failure and A Controlled Trial Investigating Outcomes of Exercise TraiNing (HF-ACTION). Am Heart J. 2013 Feb; 165(2):193-9.