HANSEN, T. A. Properties of Unfolding-based Meta-level Systems. DAIMI Report Series, [S. l.], v. 20, n. 348, 1991. DOI: 10.7146/dpb.v20i348.6578. Disponível em: https://tidsskrift.dk/daimipb/article/view/6578. Acesso em: 9 may. 2024.