1. Histologie du Systeme Nerveux, Vol;Cajal, S.;Ramon y,1952
2. Denny-Brown, D. (1928). Proc. roy. Soc. B, 103, 321.
3. Fulton, J. F., and Pi-Sunier, J. (1928). Amer. J. Physiol., 83, 554.
4. Receptors and Sensory Perception, Yale Univ;Granit, R.,1955
5. Hansen, K., and Hoffmann, P. (1922). Z. Biol., 75, 293.