Han Yo-Sub and Salomaa Arto and Salomaa Kai: Ambiguity, nondeterminism and state complexity of finite automata. In: Acta cybernetica, (23) 1. pp. 141-157. (2017)
Han Yo-Sub and Ko Sang-Ki and Piao Xiaoxue and Salomaa Kai: State complexity of Kleene-star operations on regulat tree languages. In: Acta cybernetica, (22) 2. pp. 403-422. (2015)