Factor analysis in predominantly severe COPD: identification of disease heterogeneity by easily measurable characteristics.
Postma DS, Anzueto AR, Jenkins C, Make BJ, Similowski T, Östlund O, Eriksson GS, Calverley PM. Factor analysis in predominantly severe COPD: identification of disease heterogeneity by easily measurable characteristics. Respir Med. 2013 Dec; 107(12):1939-47.