1. Airway Obstruction;Howell,1971
2. Chronic Bronchitis, Asthma, and Pulmonary Emphysema;American Thoracic Society;Amer. Rev. Resp. Dis.,1962
3. Respiratory Diseases;Crofton,1969
4. American Emphysema and British Bronchitis;Fletcher;Amer. Rev. Resp. Dis.,1964
5. Respiratory Diseases;Crofton,1969