CHENG, A.; NIELSEN, M. Open Maps, Behavioural Equivalences, and Congruences. BRICS Report Series, [S. l.], v. 3, n. 2, 1996. DOI: 10.7146/brics.v3i2.19965. Disponível em: https://tidsskrift.dk/brics/article/view/19965. Acesso em: 30 apr. 2024.