1. Adrian, E. D.: J. of Physiol. 55, 194 (1921).
2. Barcroft, J.: The respiratory function of the blood. New York: Macmillan 1928.
3. Fisher, R. A.: Statistical methods for research workers. Edinburgh 1950.
4. Fox, J. C. jun.: J. Neurosurg. 5, 531 (1949).
5. Gerard, R.W.: Arch. Neur. 40, 985 (1938).