NIELSEN, Mogens. On the Decidability of some Equivalence Problems for D0L-Systems. DAIMI Report Series, [S. l.], v. 2, n. 20, 1973. DOI: 10.7146/dpb.v2i20.6439. Disponível em: https://tidsskrift.dk/daimipb/article/view/6439. Acesso em: 19 dec. 2025.