T. Hong Loan, P. Quy Truc, D. Nguyen Phuong, T. Ai Khanh, T. Thien Thanh, and T. Dang Hoang, “STUDY ON THE BACK SCATTERING GAMMA SPECTRA OF HPGE DETECTOR BY USING MCNP CODE”, Science and Technology Development Journal, vol. 11, no. 6, pp. 61-66, Jun. 2008.