Based on your evaluation, you may decide to not use some of the sources or find additional sources. Don't get frustrated. The purpose of writing papers, speeches, and projects is for you to learn.
Research is just part of that learning process.
It is possible that you may have to use several library resources or formats of information to get the information you need. The best thing to do is allow yourself plenty of time for research. If you still aren't sure about the credibility of a source, ask a librarian or your instructor for help.