1. Task Force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology: Heart rate variability: standards of measurement, physiological interpretation and clinical use. Eur. Heart J. 17, 354–381 (1996)
2. Vanderlei, L.C.M., Pastre, C.M., Hoshi, R.A., Carvalho, T.D., Godoy, M.F.: Noções básicas de variabilidade da frequência cardíaca e sua aplicabilidade clínica. Rev. Bras. de Cir. Cardiovasc. 24(2), 205–217 (2009)
3. Tarvainen, M.P., Georgiadis, S., Lipponen, J.A., Hakkarainen, M., Karjalainen, P.A.: Time-varying spectrum estimation of heart rate variability signals with Kalman smoother Algorithm. In: 31st Annual International Conference of the IEEE EMBS, Minneapolis, Minnesota, USA, 2–6 Sept 2009
4. Heldt, T., Oefinger, M.B., Hoshiyama, M., Mark, R.G.: Circulatory response to passive and active changes in posture. Comput. Cardiol. 30, 263–266 (2003)
5. Montano, N., Ruscone, T.G., Porta, A., Lombardi, F., Pagani, M., Malliani, A.: Power spectrum analysis of heart rate variability to assess the changes in sympathovagal balance during graded orthostatic tilt. Circulation 90(4), 1826–1831 (1994)