Turnip, W. J. “Effect of Motivation and Work Environment on Employee Performance of PT. Rottela Persada Mandiri Perbaungan”. Journal of Management Science (JMAS), vol. 3, no. 1, Jan. 2020, pp. 13-18, https://www.exsys.iocspublisher.org/index.php/JMAS/article/view/43.