So for now there are almost no references, or they are hidden somewhere. May be they were once in wiki, and may be it ceased to exist for a reason, but anyway.
At first glance it may seem that by omitting them you are leaving a choice for users, but usually it is just pushing responsibility for their choices from official guides to search engines AI or third parties.
While i understand that maintaining reference list is hard, and there are conflicts about every link, a conscious choice can be made only by personally comparing possible variants.
Including links to books, blogs etc is overkill, but categorized official list of open-source gems would be super useful.