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2. Global Surveillance, Prevention and Control of Chronic Respiratory Diseases: A Comprehensive Approachhttp://www.who.int/gard/publications/GARD%20Book%202007.pdf
3. Characteristics of breath sounds and adventitious respiratory sounds;Sovijarvi;Eur. Respir. Rev.,2000
4. Pulmonary auscultation;Karnath;Hosp. Physician,2002
5. Peak expiratory flow: conclusions and recommendations of a working party of the european respiratory society;Quanjer;Eur. Respir. J.,1997