Ổn, Phùng Văn. “on the Complexity of Recognition of Regular Layer Languages Generating by Extended Hyper Generating-Schemas”. <i>Journal of Computer Science and Cybernetics</i> 20, no. 2 (July 25, 2012): 176–182. Accessed November 4, 2025. https://jcc.vast.vn/jcc/article/view/1474.