Some methodological issues in chronic illness research.
D002908:Chronic Disease; D002986:Clinical Trials as Topic / Q000379:methods*; D003625:Data Collection / Q000379:methods; D004185:Disability Evaluation; D006801:Humans; D007407:Interviews as Topic; D008173:Lung Diseases, Obstructive / Q000503:physiopathology; D012107:Research Design