“δ-SHOCK MAINTENANCE MODEL FOR AN IMPROVING SYSTEM UNDER PARTIAL SUM PROCESS” (2020) INTERNATIONAL JOURNAL OF MATHEMATICS (IJMM), 1(1), pp. 1–11. Available at: https://iaeme-library.com/index.php/IJMM/article/view/IJMM_01_01_001 (Accessed: 30 March 2026).