Surganingsih, M., A. . Amal, N. I. Ramadani, F. Afifah, and F. E. Suras. “Cognitive Development: Enhancing Classification Skills in 5- to 6-Year-Olds Through Structured Manipulative Learning”. Ihya Ulum: Early Childhood Education Journal, vol. 4, no. 1, Mar. 2026, pp. 685-96, doi:10.59638/ihyaulum.v4i1.811.