Imreh, Balázs, and Masami Ito. “On Regular Languages Determined by Nondeterministic Directable Automata”. Acta Cybernetica 17, no. 1 (January 1, 2005): 1-10. Accessed April 25, 2024. https://cyber.bibl.u-szeged.hu/index.php/actcybern/article/view/3650.