Name	Info	Provider	Link
	subscription/membership/fee required	American Physical Society	https://link.aps.org/abstract/PRL/v108/p193201
	free resource	PubMed Central	https://www.ncbi.nlm.nih.gov/pmc/articles/pmid/23003037/
	free resource	Europe PubMed Central	https://europepmc.org/abstract/MED/23003037