Abano, E. E., L. K. Sam-Amoah, and A. Bart-Plange. “Variation in Ultrasonic Frequency and Time As Pre-Treatments to Air-Drying of Carrot”. Journal of Agricultural Engineering, vol. 43, no. 4, Mar. 2013, p. e23, doi:10.4081/jae.2012.e23.