F. A. Jamal Mohamad, Anita Ahmad, Ruzairi Abdul Rahim, Sallehuddin Ibrahim, Juliza Jamaludin, and Noorhazirah Sunar, “The Identification of Optimal Frequency for Ultrasonic Transducers in Concrete-Defect Detection using COMSOL® Simulator”, Elektrika, vol. 24, no. 2, pp. 104–110, Aug. 2025.