Peerapatana Ketboonchoo และ Napassavong Osothsilp. (2006) The service duration improvement in service industry through the approach of lean six SIGMA : a case study of Pattana Medical Center. Chulalongkorn University:ม.ป.ท.Peerapatana Ketboonchoo และ Napassavong Osothsilp. 2006. The service duration improvement in service industry through the approach of lean six SIGMA : a case study of Pattana Medical Center. ม.ป.ท.:Chulalongkorn University;Peerapatana Ketboonchoo และ Napassavong Osothsilp. The service duration improvement in service industry through the approach of lean six SIGMA : a case study of Pattana Medical Center. ม.ป.ท.:Chulalongkorn University, 2006. Print.