Name	Info	Provider	Link
	free resource	Korean Academy of Medical Sciences	https://jkms.org/DOIx.php?id=10.3346/jkms.2010.25.3.489
Endoscopy	free resource	MedlinePlus Health Information	https://medlineplus.gov/endoscopy.html
	free resource	PubMed Central	https://www.ncbi.nlm.nih.gov/pmc/articles/pmid/20191054/
	free resource	Europe PubMed Central	https://europepmc.org/abstract/MED/20191054