2 × 9 = 81 conversely and 9 × 9 = 18 conversely” Mathematic play of 9- year-old, the copyright and the civil law. Dyskurs Prawniczy i Administracyjny [Internet]. 2024 Mar. 4 [cited 2025 Dec. 14];(1). Available from: https://www.dyskurs.inp.uz.zgora.pl/index.php/DPiA/article/view/414