Aisyah, S. .; Natasha, S. F. .; Risal, T. .; Rizki, S. .; Dewi, A. F. .; Saragih, N. M. . Analysis of the Effectiveness of Implementing Internal Control on Doubtful Receivables PT. PLN Persero ULP Belawan. MINISTAL 2023, 2, 1175-1186.