Dhandio, D. J.; Sulistianingsih, E.; Satyahadewi, N. INTEGRATION OF DAVIES-BOULDIN INDEX VALIDATION AND MEAN-VARIANCE EFFICIENT PORTFOLIO IN K-MEANS++ CLUSTERING FOR OPTIMIZATION OF THE LQ45 STOCK PORTFOLIO. BAREKENG: J. Math. & App. 2025, 19, 2609-2620.