Name	Info	Provider	Link
	free resource	Primary Care Respiratory Society UK	https://doi.org/10.1038/pcrj.2003.3
	free resource	PubMed Central	https://www.ncbi.nlm.nih.gov/pmc/articles/pmid/31700334/
	free resource	Europe PubMed Central	https://europepmc.org/abstract/MED/31700334