E. T. B. Nainggolan, A. A. Waruwu, and A. Setiawan, “The Influence of Motivation and Work Discipline on employee Performance at PT Perkebunan Nusantara IV Regional 1 Medan”, J. Manag. Econ. Account., vol. 5, no. 4, pp. 2621–2628, Oct. 2026.