Luong, D.-T., T.-L. Vu Thi, and T.-N. Dang. “A Lagrange Function Approach to Study Second-Order Optimality Conditions for Infinite-Dimensional Optimization Problems”. HPU2 Journal of Science: Natural Sciences and Technology, vol. 4, no. 01, Apr. 2025, pp. 20-30, doi:10.56764/hpu2.jos.2025.4.01.20-30.