Hidayat, T. P. “The Influence of Communication, Work Discipline and Work Environment on Employee Performance at PT. PLN (Persero) South Medan Customer Service Unit (ULP)”. Jurnal Sains Dan Teknologi, vol. 5, no. 1, Sept. 2023, pp. 313-9, https://ejournal.sisfokomtek.org/index.php/saintek/article/view/1619.