Trung, Mai Xuân, et al. “ESTABLISH A CALIBRATION EFFICIENCY IN GAMMA SPECTROMETERS AND EVALUATE EFFICIENCY CURVES IN COMMERCIAL SOFTWARE”. Dalat University Journal of Science, vol. 1, no. 1,2,3,&4, Sept. 2011, pp. 81-90, https://doi.org/10.37569/DalatUniversity.1.1,2,3,&4.170(2011).