Most dead-tree sources can be found a good library, which should be
enough to verify it if we need to.
Know anyone who has ever gone to a library to verify a Wikipedia citation? Ever had a suspicion about a dead-tree citation? Could you be bothered going to a library to check it out? Could you be bothered to click on a link?
Yes to all four. But it was to check out a citation in a book I wanted to read anyway, and also it should be noted that I am a freak.
In a different case, there was an article on an obscure topic that was plausible, had proper-looking references to both online and offline sources written by subject-matter experts, and turned out to be total [[WP:BOLLOCKS]].
It was frustrating not to have access to some of the sources, but luckily in this case the paper copies weren't needed. It was challenged it while the article authors (or, likely, one author with multiple socks) were still writing it, so they were there to answer requests to quote the relevant passages; they also had a talent for self-conviction.
If it had been some time after the fact, it may have been a different story, and the article might still exist. I don't know that I would have bothered to track it down myself. It's not even clear I would even have successfully navigated AfD, which was hard enough as it was. It has been my only AfD listing since I started on... well, look at that, four years yesterday, virtual happy birthday to me.
Dan