อ้างอิง ของ ซิกส์ซิกมา

  1. ↑ Davis R. Bothe, 2002, "Statistical Reason for the 1.5s Shift", Quality Engineering, issue 14, Vol 3, pp479-487
  2. ↑ Joseph A. De Feo & William Barnard. JURAN Institute's Six Sigma Breakthrough and Beyond - Quality Performance Breakthrough Methods, Tata McGraw-Hill Publishing Company Limited, 2005. ISBN 0-07-059881-9