The website FindArticles.com was a great website which was functional until late 2012. It archived journal articles, newspapers and books of all sorts. At this pont in time Wikipedia has over 20 000 links to FindArticles.com, most of the as sources and references. The only downsides is that the website is dead. Most times when a link dies they are archived on other websites such as arhvie.org (the Wayback machine), and this website was, until September 2012. At that time the websites robot.txt was changed, and all archived copies on websites which follows web etiquette was deleted. The website isn’t marked as 404 either, which makes it hard for tools to mark the links as dead too.
Most of the links from Wikipedia to FindArticles are for journal articles, which most likely has doi’s or pmid’s, but not mentioned in the articles. Thes casues some problems. Either remove all links to FindArticles.com with any though of the consequences, or look at each article one-by-one and try to find another copy of the journal online or identification numbers and then remove the links.
Normally you could run the bot Citation bot on incompleat citation and have it fill out and find information which is not already in the reference, however the bot is currently blocked due to Wikimedia’s decition to change to https without real consideration of how it would break all tools currently in place for day-to-day operatons.