Gaya APA

, A, S., Khoil, M. (2013). Six Sigma: Quality for Business Improvement (Pertama). Yogyakarta: Graha Ilmu.

Gaya MLA

, Amin, Syukron., Khoil, Muhammad. "Six Sigma: Quality for Business Improvement ". Pertama Yogyakarta: Graha Ilmu, 2013. .