TY  - RPRT
TI  - Aetiological factors in persistent sputum production: a case-control study.
AU  - P Cullinan
PY  - 1993
DO  - 10.1136/jech.47.1.27
UR  - https://pubmed.ncbi.nlm.nih.gov/8436888/
ID  - 8436888
ER  -