BLOOM, S. L.; ÉSIK, Z. An Extension Theorem with an Application to Formal Tree Series. BRICS Report Series, [S. l.], v. 9, n. 19, 2002. DOI: 10.7146/brics.v9i19.21736. Disponível em: https://tidsskrift.dk/brics/article/view/21736. Acesso em: 24 apr. 2024.