W. Febrianti, N. Sumarti, A. S. Nasution, A. Fitriawati, D. E. P. Siregar, and Y. S. S, “Optimizing ESG-Constrained Mean-Variance Portfolio using Spiral Optimization Algorithm”, J. Multidiscip. Appl. Nat. Sci., vol. 6, no. 2, pp. 1146–1159, Apr. 2026.