Koshiba, Takeshi, Erkki Mäkinen, and Yuji Takada. “Inferring Pure Context-Free Languages from Positive Data”. Acta Cybernetica 14, no. 3 (January 1, 2000): 469-477. Accessed June 8, 2023. https://cyber.bibl.u-szeged.hu/index.php/actcybern/article/view/3540.