Breadth-first serialisation of trees and rational languages
  We present here the notion of breadth-first signature and its relationship with numeration system theory. It is the serialisation into an infinite word of an ordered infinite tree of finite degree. We study which class of languages corresponds to which class of words and,more specifically, using a known construction from numeration system theory, we prove that the signature of rational languages are substitutive sequences. 
Victor Marsault and Jacques Sakarovitch
cs.FL