Irreducible complexity of iterated symmetric bimodal maps
  We introduce a tree structure for the iterates of symmetric bimodal maps and identify a subset which we prove to be isomorphic to the family of unimodal maps. This subset is used as a second factor for a $\ast $-product that we define in the space of bimodal kneading sequences. Finally, we give some properties for this product and study the *-product induced on the associated Markov shifts. 
J. P. Lampreia, R. Severino, J. Sousa Ramos