Six sigma(Quality control standard)

Design for Six sigma by: Launsby, Robert G.; Brue, Greg (Language materials, printed)

Statistics for six sigma green belts with Minitab and JMP by: Levine, David M. (Language materials, printed)

Six sigma for marketing processes : an overview for marketing executives, leaders, and managers by: Hambleton, Lynne; Creveling, Clyde M.; McCarthy, Burke (Language materials, printed)