RT Journal Article SR Electronic T1 Sputum production in chronic cough increases the probability of asthma: a cross-sectional questionnaire study JF ERJ Open Research JO erjor FD European Respiratory Society SP 00086-2021 DO 10.1183/23120541.00086-2021 VO 7 IS 2 A1 Heikki O. Koskela A1 Anne M. Lätti YR 2021 UL http://openres.ersjournals.com/content/7/2/00086-2021.abstract AB