Retningjati, Ajeng, Lydia Yunita, and Martua sitorus. 2018. “Effect of Competence And Work Motivation on Employee Performance PT. Rotella Mandiri Persada Perbaungan”. Journal of Management Science (JMAS) 1 (2, April):36-40. https://exsys.iocspublisher.org/index.php/JMAS/article/view/7.