ÉSIK, Z.; LEISS, H. Greibach Normal Form in Algebraically Complete Semirings. BRICS Report Series, [S. l.], v. 9, n. 46, 2002. DOI: 10.7146/brics.v9i46.21761. Disponível em: https://tidsskrift.dk/brics/article/view/21761. Acesso em: 29 nov. 2022.