Aceto L, Fokkink WJ, Ingólfsdóttir A. On a Question of Arto Salomaa: The Equational Theory of Regular Expressions over a Singleton Alphabet is not Finitely Based. BRICS [Internet]. 6. juni 1996 [henvist 5. december 2025];3(36). Tilgængelig hos: https://tidsskrift.dk/brics/article/view/20018