S. Siswanto, Dewi Yustiana, Koen Irianto Uripan, S. Sutomo, and Siti Nur Soleha, “The Effect of Competency Certification on Employee Performance with Competency Testing as a Variable Mediation (Study at PT. X)”, Jurnal Ekonomi, vol. 15, no. 01, pp. 14–29, Jan. 2026.