Khatayos Phummanee และ Somkiat Tangjitsitcharoen. (2015) IMPROVEMENT OF PREVENTIVE MAINTENANCE PLAN OF NEW ELEVATOR PRODUCT. Chulalongkorn University:ม.ป.ท.Khatayos Phummanee และ Somkiat Tangjitsitcharoen. 2015. IMPROVEMENT OF PREVENTIVE MAINTENANCE PLAN OF NEW ELEVATOR PRODUCT. ม.ป.ท.:Chulalongkorn University;Khatayos Phummanee และ Somkiat Tangjitsitcharoen. IMPROVEMENT OF PREVENTIVE MAINTENANCE PLAN OF NEW ELEVATOR PRODUCT. ม.ป.ท.:Chulalongkorn University, 2015. Print.