There are many case studies on oligopolies present in India. An oligopoly is an economic system where a few elite groups or individuals control the industry. It is similar to a monopoly in that the power in the industry is heavily concentrated, but there is still competition between those groups.
It seems that the oligopoly surrounding the automotive industry in India is well studied. I've attached some examples of case studies and examinations of the automotive oligopoly at the bottom of this post.
Additionally, there is oligopoly in other industries. I've attached a case study on the oligopoly surrounding the airline industry at the bottom of this post as well.
There are certainly many other oligopolies and industries to examine. In fact, oligopoly almost certainly exists in some form in every capitalistic nation in Earth, so there are plenty of other case studies to understand how they operate.