Gupta, P. (2004). Six sigma business scorecard. McGraw-Hill.
Lua i Stíl Chicago (17ú heag.)Gupta, Praveen. Six Sigma Business Scorecard. McGraw-Hill, 2004.
Lua MLA (8ú heag.)Gupta, Praveen. Six Sigma Business Scorecard. McGraw-Hill, 2004.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.