Examples of research resources for which Wikipedia is known as being amongst top referrers? Wikimedia sites &ndash; and Wikipedias in particular &ndash; direct a lot of traffic to many web resources, including research-related ones. 

Click stream data is not recorded on the Wikimedia end, so the alternative approach to finding out how important Wikimedia sites are in terms of traffic to research resources is analyzing the latter's referral logs. 

One such analysis that was made public is from CrossRef. I am looking for other cases where such analyses have been made public. 

Interesting questions to ask about such datasets:


Is wikipedia.org or one of its sister or subdomains (e.g. wikimedia.org or en.wikipedia.org) amongst the top referrers?
Is that pattern stable?
Since when has this been the case?
What are/might be the main drivers of that traffic (in the case of CrossRef, it's Wikipedia readers clicking on references cited by their respective DOIs)?
This doesn't directly answer your question, but in 2012, the Biodiversity Heritage Library's then-technical director published a presentation reporting on how users from Wikipedia stayed longer and browsed deeper than others, which included some analytics information. You could drop the the BHL an e-mail and see if they'd be interested in sharing any more recent details.