You can take the reference book into the exam: Benbow, Donald W., and T.M. Kubiak, The Certified Six Sigma Black Belt Handbook, Milwaukee, WI: ASQ Quality Press, 2005.
As it is an open book test as I remember it.
I would recommend the QCI Primer on CSSBB, Quality Toolbox, and The Quality Improvement Glossary. These helped me on the exam as well.
Good question.
Eric