Hartmann, Sven, Sebastian Link, and Klaus-Dieter Schewe. “Functional Dependencies over XML Documents With DTDs”. Acta Cybernetica 17, no. 1 (January 1, 2005): 153-171. Accessed April 24, 2024. https://cyber.bibl.u-szeged.hu/index.php/actcybern/article/view/3659.