Fyath, R. S., and Zahraa M. Ali Kamil. “Investigation of Raman Amplification In Photonic Crystal Fibers”. Nahrain University College of Engineering Journal, vol. 11, no. 3, Dec. 2008, pp. 511-2, https://oldjournal.eng.nahrainuniv.edu.iq/index.php/main/article/view/552.