@article{WesselRiedlKurths2009,
  author    = {Niels Wessel and Maik Riedl and J{\"u}rgen Kurths},
  title     = {Is the normal heart rate "chaotic" due to respiration?},
  doi       = {10.1063/1.3133128},
  url       = {http://ojps.aip.org/chaos/},
  year      = {2009},
}