Shin-Jye Lee. “A Brief Concept of Natural Language Processing: The Chomsky Hierarchy and Hidden Markov Models”. iJournals:International Journal of Software & Hardware Research in Engineering ISSN:2347-4890 9, no. 6 (June 29, 2021). Accessed May 9, 2026. https://ijournals.in/journal/index.php/ijshre/article/view/40.