Vĩnh, H. N., P. T. Huy, and Đỗ L. Vân. “Extension of Codes and Algorithms for Alternative Codes and Codes of Bounded Words”. Journal of Computer Science and Cybernetics, vol. 26, no. 4, Apr. 2012, pp. 301-1, doi:10.15625/1813-9663/26/4/504.