Nisa, K., Sarifah, I., & Riyadi, R. (2026). COMBINATION OF CONTENT VALIDITY INDEX AND FUZZY DELPHI FOR EXPERT VALIDATION OF A THREE-TIER MATHEMATICS LEARNING DIFFICULTIES DIAGNOSTIC ASSESSMENT. BAREKENG: Jurnal Ilmu Matematika Dan Terapan, 20(4), 3423-3436. https://doi.org/10.30598/barekengvol20iss4pp3423-3436