1. Sur les mots sans carré définis par un morphisme;Berstel,1979
2. A. Ehrenfeucht and G. Rozenberg. On subword complexities of homomorphic images of languages, Rev. Fr. Automat. Inform. Rech. Opér., Sér. Rouge, to appear.
3. A. Ehrenfeucht and G. Rozenberg, On the subword complexity of square-free DOL languages, Theoret. Comput. Sci., to appear.
4. The Mathematical Theory of L Systems;Rozenberg,1980
5. Morphisms on free monoids and language theory;Salomaa,1980