TY  - RPRT
TI  - Visible expiratory valves.
AU  - T N Munro
PY  - 1989
DO  - 10.1111/j.1365-2044.1989.tb09224.x
UR  - https://pubmed.ncbi.nlm.nih.gov/2618999/
ID  - 2618999
ER  -