A Copying Theorem for ETOL Languages with Rank
Grzegorz Rozenberg, Dirk Vermeir · Fundamenta Informaticae · 1981
An infinite hierarchy within the class of ETOL languages is proved in such a way that it is spanned on an infinite sequence of ETOL languages with increasing rank where each of the languages has a length set containing the range of a strictly growing polynomial of degree 1.