Zachar, Z. “On the Equivalence of the Frontier-to-Root Tree Transducers I.”. Acta Cybernetica 7, no. 2 (January 1, 1985): 173-182. Accessed December 26, 2024. https://cyber.bibl.u-szeged.hu/index.php/actcybern/article/view/3285.