Al-Badran, Adnan, and Sabaa Al-Fadal. “Cloning, Expression of Hirudin Gene from Leech (Hirudo Orientalis) in BL21(DE3) Strain”. American Scientific Research Journal for Engineering, Technology, and Sciences, vol. 27, no. 1, Jan. 2017, pp. 25-42, https://asrjetsjournal.org/American_Scientific_Journal/article/view/2511.