U. A. Adam, T. Owolabi, S. Lameed, C. Ubaka, and A. T. Joy, “Decoding Difficulty: A Quantitative Analysis of Difficult Concept in the Biology Curriculum”, JES, vol. 8, no. 4, pp. 570–581, Oct. 2024, doi: 10.31258/jes.8.4.p.570-581.