V. L. Bui, V. Q. Nguyen, T. A. Le, V. B. Nguyen, T. H. Bui, and C. T. Nguyen, “Enrichment determination of low – enriched uranium material by gamma spectroscopic method”, Nucl. Sci. and Tech., vol. 4, no. 2, pp. 1-6, Jun. 2014.