R. Widdhiharto, N. Isaeni, S. Mayangwuri, R. C. I. Prahmana, and S. A. Widodo, “Data-Driven Profiling of Teachers’ Competence in Numeracy Instruction: K-Means Clustering Analysis of ‘Gembira’ Training Participants”, J. ris. pendidik. mat, vol. 13, no. 1, Jun. 2026.