Oligarchy is a system of government in which power is shared by a privileged few. Theoretically or ideally, the individuals sharing power would be considered the wisest of the populace. The concept of oligarchy descends from the Greeks. The government of Sparta was an oligarchy, while neighboring Athens had a democracy. In contrast to the democracy, Sparta was ruled by a few and not everyone.
There have not been many examples of oligarchies in history or literature. If you are looking for an article describing an actual working oligarchy today, that might be difficult. If you just want articles that mention the term, I have included some below.