T. H. Cao, H. C. . Nguyen, X.-C. . Dang, C. T. . Chu, T. A. . Le, and T. T. H. . Le, “Exploring Numeracy Skills of Lower Secondary School Students in Mountainous Areas of Northern Vietnam”, IJLTER, vol. 21, no. 10, pp. 309–324, Oct. 2022.