1. Transductions and Context-Free Languages;Berstel,1979
2. Ordres et types de langage, I, II, III;Boasson;Notes CRAS, série A,1977
3. Ordres et types de langage, I, II, III;Boasson;Notes CRAS,1977
4. Ordres et types de langage, I, II, III;Boasson;Notes CRAS,1977
5. The rational index, a complexity measure for languages;Boasson;SIAM J. Comput.,1981