R. Movasaghi, F. Salehpour, A. Ahmadvand, D. Agha-Mohammadi, A. A. Dorosty, and R. Vafaee, “The effect of epidural morphine sponge in postoperative pain control after Microdiscectomy”, Arch Adv Biosci, vol. 3, no. 4, Sep. 2012.