“Modeling the Competitiveness of Indonesian Palm Oil Industry: A Conceptual Model Using Hierarchical Multi-Level System Approach”. Jurnal Teknik Industri: Jurnal Keilmuan Dan Aplikasi Teknik Industri, vol. 15, no. 2, Dec. 2013, pp. 103-10, https://doi.org/10.9744/jti.15.2.103-110.