@article{Guzik:2010,
  author  = "P. Guzik and J. Piskorski and T. Krauze and A. Wykrętowicz and H. Wysocki",
  title   = "Partitioning total heart rate variability",
  journal = "International Journal of Cardiology",
  volume  = "Vol. 144",
  number  = "no. 1",
  pages   = "138--139",
  year    = "2010",
  note    = "[Letter to the Editor]",
}