Purwaningsih, Ratna, Christoper Frans Simanjuntak, and Zainal Fanani Rosyada. 2020. “Eco-Efficiency of Pencil Preduction Using Life Cycle Assessment to Increase the Manufacture Sustainability”. Jurnal Teknik Industri: Jurnal Keilmuan Dan Aplikasi Teknik Industri 22 (1):47-54. https://doi.org/10.9744/jti.22.1.47-52.