R. W. Dal Negro, S. Tognella, M. Guerriero, and C. Micheletto, “Prevalence of tracheobronchomalacia and excessive dynamic airway collapse in bronchial asthma of different severity”, Multidiscip Respir Med, vol. 8, no. 9, Mar. 2013, doi: 10.4081/mrm.2013.509.