“SUSTAINABLE DEVELOPMENT OF 21ST CENTURY SKILLS IN MATHEMATICS EDUCATION USING HEURISTIC AND PROBLEM-SOLVING TECHNIQUES” (2022) International Journal of Food and Nutritional Sciences, 11(13), pp. 2709–2718. Available at: https://www.ijfans.org/index.php/Journal/article/view/7778 (Accessed: 12 August 2026).