Berghammer, Rudolf. “On the Characterization of the Integers : The Hidden Function Problem Revisited”. Acta Cybernetica 11, no. 1-2 (January 1, 1993): 85-96. Accessed March 29, 2024. https://cyber.bibl.u-szeged.hu/index.php/actcybern/article/view/3421.