Wang CN, Nguyen XT. A Hybrid Approach for Measuring Productivity in the Global Fitness Industry by Using Grey and DEA Model. ASRJETS-Journal [Internet]. 2017 Nov. 15 [cited 2024 Apr. 28];38(1):33-47. Available from: https://asrjetsjournal.org/index.php/American_Scientific_Journal/article/view/3591