Castaldi PJ, Benet M, Petersen H, Rafaels N, Finigan J, Paoletti M, Marike Boezen H, Vonk JM, Bowler R, Pistolesi M, Puhan MA, Anto J, Wauters E, Lambrechts D, Janssens W, Bigazzi F, Camiciottoli G, Cho MH, Hersh CP, Barnes K, Rennard S, Boorgula MP, Dy J, Hansel NN, Crapo JD, Tesfaigzi Y, Agusti A, Silverman EK, Garcia-Aymerich J. Do COPD subtypes really exist? COPD heterogeneity and clustering in 10 independent cohorts. Thorax. 2017 11; 72(11):998-1006.