ACETO, L.; ÉSIK, Z.; INGÓLFSDÓTTIR, A. A Fully Equational Proof of Parikh’s Theorem. BRICS Report Series, [S. l.], v. 8, n. 28, 2001. DOI: 10.7146/brics.v8i28.21688. Disponível em: https://tidsskrift.dk/brics/article/view/21688. Acesso em: 28 mar. 2024.