1. Allison, R. D. (1968) The role of impedance plethysmography in biomedical research and diagnostic medicine.Bio. Med. Eng.,4, 500–503.
2. Brodie, T. G. andRussell, A. E. (1905) On the determination of blood flow through an organ.J. Physiol. 45, 31–32.
3. Burton, A. C. (1939) The range and variability of blood flow in the human fingers and the vasomotor regulation of body temperature.Am. J. Physiol.,127, 437.
4. Couch, N. P., Van der Water, J. M. andDmochowski, J. R. (1971) Non-invasive measurement of peripheral arterial flow.Arch. Surg. 102, 435–439.
5. Folse, R. andAlexander, R. H. (1970) Directional flow detection for localising venous valvular incompetency.Surgery 67, 114–121.