U. Silalahi, J. Z. F. Saragih, F. X. Tjipto, D. E. Damanik, and N. E. Hutagaol, “Licensing Procedures for Palm Oil Mills in North Sumatra: Integration of Investment Law and Regional Ecological Impacts”, Pol. Law Not. Regul. Issues, vol. 5, no. 2, pp. 376–390, May 2026.