1. Pierangelo B. Errors in laboratory medicine. Clin Chem. 2002;48:691-698.
2. For definition of the Five Why tool, go to http://www.asq.org/sixsigma/terms/index.html
3. Michael, G. The Lean Six Sigma Pocket Tool Book. New York, NY: McGraw Hill; 2005: 2.
4. Trusko B, Pexton C. Improving Healthcare Quality & Cost with Six Sigma. Upper Saddle River, NJ: FT Press; 2007:378.