There is no reason to believe that Wikipedia articles are authoritative. They are likely to be correct, but you cannot be sure. So they are a good place to start, but not the place you reference in a scholarly article (unless you are writing about Wikipedia articles!)
In general, you are likely to misled by most internet sources, unless they are manifestly professional and well documented. Books and journals, still, are the main sources. I am quite willing to believe that in a decade the internet and its devices will become more reliable, and also more unreliable. You might want to use Google Scholar, but keep in mind that many of the leads there are to preprints or other unrefereed articles.
If you are very experienced, you can actually find good stuff. And in general, for a date or a name the internet is useful.
A student came into my office talking about the Grameen Bank, microcredit lending. I asked if they knew of criticism of the institution. No response. So I went to Wikipedia under "Grameen Bank", and there was a section on criticism of the innovation. Surely, this is not complete, and I don't know if the sources are good ones. BUT it can start me off, and it will lead me into the literature. That's what I need. I would not refer to the internet source, Wikipedia, but I would check and then refer to the original articles.
More generally, most students, undergraduate and graduate, as well as high school, are insufficiently sophisticated to use internet sources, but those sources are so readily available to them they are irresistible. Hence, teachers tell their students of the problems of internet sources, but rarely their advantages: ready availability, a good place to start (but NOT end), and quick and dirty orientation to a subject. The internet and Wikipedia replace the Encyclopedia Britannica or Encyclopedia Americana (which claimed authority, and which worked at keeping errors down), but the internet in general has no monitor. As for dictionaries, you are best off with one of the standards, such as the Webster's Third New International Dictionary (1961) or the Oxford English Dictionary=OED, a multivolume work. They too are on the internet, in part behind pay walls, but many colleges and universities have site licenses.
If you want to have fun, look at one of the older editions of the encyclopedias. I have a post-WWI edition of the Britannica, part of the tradition of longer authoritative articles written by putative experts.
The most important feature of a desktop dictionary is that it be light enough so that you are willing to check it as often as you wish to. Hence, you may prefer a concise or otherwise abridged dictionary, a college edition, for example. The great advantage of a book, or of going to the library stacks, is that you find things you were not looking for that were adjacent to what you were looking for. And in the case of books, you can, much as did Augustine, open up a book anywhere and see what's there. For Augustine, it was the New Testament, and what he heard in the voices of children or perhaps the leaves in the wind was tolle lege, namely, "take it and read." And so he opened up the NT and found what he needed to hear to make him become the Christian his mother Monica had been urging on him for a very long time.
