References
- Autebert , J. M. and Boasson , J. 1988 . Transductions Rationelle , Masson .
- Berstel J. Transductions and Context Free Languages Teubner 1979
- Ginsburg , S. and Greibach , S. 1970 . Principal AFL . J. Computer System Sci. , 4 : 308 – 338 .
- Ginsburg , S. and Greibach , S. 1969 . Abstract families of languages: in Studies in Abstract families of languages . Mem. Amer. Math. Soc. , 87 : 41 – 51 .
- Ginsburg , S. and Spanier , E. H. 1970 . Substitution in families of languages . Inf. Sci. , 2 : 83 – 110 .