Invariants for the topological characterization of the iteration of differentiable functions – the bimodal caseM.F. Correia, C.C. Ramos and S.M. VinagreEur. Phys. J. Special Topics, 222 2 (2013) 285-301DOI: https://doi.org/10.1140/epjst/e2013-01842-y