Rohmadi, A., R. Saptono, B. Hendrasuryawan, B. Widoyono, and A. Syaifuddin. “Content-Based Recommendation System for Non-Textbook Using TF-IDF, Cosine Similarity, and Educational Level Filtering”. Jurnal Teknik Informatika (Jutif), vol. 7, no. 4, Aug. 2026, pp. 3557-68, doi:10.52436/1.jutif.2026.7.4.5425.