O. M. Yahya, عمر, B. A. Ahmed, بیداء, I. Thanoon, and عماد, “Ultrasound-assisted one-pot synthesis of dihydropyrimid-2-one/thiones catalyzed by zirconyl chloride hexahydrate”, EDUSJ, vol. 26, no. 5, pp. 154–159, Dec. 2013.