The expressibility of languages and relations by word equations... In particular, "the primitiveness" and "the equal length" are such properties, as well as being "any word over a proper subalphabet"
Nonterminals versus homomorphisms in defining languages for some classes of rewriting systems ; cu-cs-027-73...(its alphabet, the set of productions and the axiom) one can define the language of G by (i) taking out of all stings generated by G only those which are over a distinguished subalphabet of G, or (ii) translating the set of all strings generated by G by a fixed homomorphism....
Transitive factorizations of free partially commutative monoids and lie algebras... We give here anecessary and sufficient condition on a subalphabet $B\subset A$ such that theright factor of a bisection $\M(A,\theta)=\M(B,\theta\_B).T$...
Lazard's elimination (in traces) is finite-state recognizableWe prove that the codes issued from the elimination of any subalphabet in atrace monoid are finite state recognizable....
