Most research papers fall into one of three categories: analytical, expository, or argumentative. If you’re presenting an analysis of information, then your paper is analytical. If you’re writing to explain information, then your paper is expository. If you’re arguing a conclusion, then it’s argumentative or persuasive. Your thesis statement should match the type of paper you’re writing.
Any information that doesn’t fit within the framework of your outline, and doesn’t directly support your thesis statement, no matter how interesting, doesn’t belong in your research paper. Keep your focus narrow and avoid the kitchen sink approach. (You know, the one where you throw in every bit of interesting research you uncovered, including the fungal growth in the U-joint of your kitchen sink?) Everything you learn may be fascinating, but not all of it is going to be relevant to your paper.
If you find one really awesome book or journal that fits your topic perfectly, try looking in the works cited/bibliography/reference list at the end of it. This should contain many more books and journals that are about your topic as well.
Take a trip to your local library or university library. Although it may seem old fashioned, libraries are chock full of helpful research materials from books to newspapers and magazines to journals. Don’t be afraid to ask the librarian for help either - they are trained in research and know where everything about your topic is located.