An approach to comparing Kolmogorov-Sinai and permutation entropy V.A. Unakafova, A.M. Unakafov and K. Keller Eur. Phys. J. Special Topics, 222 2 (2013) 353-361 Published online: 25 June 2013 DOI: 10.1140/epjst/e2013-01846-7