Natural coefficients and invariants for Markov-shifts. Klaus Schmidt, William Parry (1984) Inventiones mathematicae
Non-hyperbolicity and invariant measures for unimodal maps Tomasz Nowicki, Sebastian Van Strien (1990) Annales de l'I.H.P. Physique théorique
Numerical invariants of exponential groups and locally free approximation of the braid group. Vershik, A.M. (2000) Zapiski Nauchnykh Seminarov POMI