1. H.J. Schmitt et al., Note on the generation of breathing related subharmonics in arterial PPG rhythms, in Proc. 8th Int. Symp. CNVD 1998, VDI, Düsseldorf, ISBN 3-18-330020-6, pp. 41–48 (1999)
2. M.M. Rao et al., Influence of controlled breathing (PRANAYAMA) on dermal perfusion as monitored by optical sensors, in Proc. 8th Int. Symp. CNVD 1998, VDI, Düsseldorf, ISBN 3-18-330020-6, pp. 49–55 (1999)
3. D. Hoyer et al., Nonlinear dynamics of the cardio respiratory system. IEEE Eng. Med. and. Biol. 12, 16–61 (1998)
4. C. Newiger, Osteopathie. TRIAS-1999, Verb. der Osteopathie Deutschland, (1999)
5. H.J. Schmitt et al., Low frequency blood volume rhythms: possible origins and new mea-surements, in Proc. 9th Int. Symp. CNVD 2000, VDI, Düsseldorf, ISBN 3-89653-881-0, pp. 99–104 (2001)