Karhumäki, Juhani, Aleksi Saarela, and Luca Q. Zamboni. “Variations of the Morse-Hedlund Theorem for K-Abelian Equivalence”. Acta Cybernetica 23, no. 1 (January 1, 2017): 175-189. Accessed August 4, 2020. https://cyber.bibl.u-szeged.hu/index.php/actcybern/article/view/3921.