Quantifying heart rate dynamics using different approaches of symbolic dynamicsD. Cysarz, A. Porta, N. Montano, P.V. Leeuwen, J. Kurths and N. WesselEur. Phys. J. Special Topics, 222 2 (2013) 487-500DOI: https://doi.org/10.1140/epjst/e2013-01854-7