Before you dive into a research paper, it can be a good idea to do some background research. This will help you figure out a topic that is interesting to you, and introduce you to the major players in your particular area.
Many people do background research through sources like Wikipedia or general Google searching. You can also use a variety of specific encyclopedias that are available through the MSU Libraries.
The premiere legal encyclopedia is American Jurisprudence 2d (AMJUR). It is made up of many volumes and can be found in print at the MSU Law Library, for in-library use. There is also this electronic version found in NexisUni:
An additional general legal source to try:
Political Science resources that have proven helpful on the topic of impeachment: