Name	Info	Provider	Link
	subscription/membership/fee required	Elsevier Science	https://linkinghub.elsevier.com/retrieve/pii/S0035-9203(08)00060-6
	subscription/membership/fee required	Silverchair Information Systems	https://academic.oup.com/trstmh/article-lookup/doi/10.1016/j.trstmh.2008.02.007