1. Southwell, R. V., J. Roy. Aero. Soc., 29, 146 (1925).
2. Ower, E., Measurement of Air Flow (Chapman and Hall, 1927, 1943, 1949; Pergamon, 1966).
3. Pankhurst, R. C., and Holder, D. W., Wind Tunnel Technique (Pitman, 1952 and 1965).
4. Frazer, R. A., and Duncan, W. J., A.R.C. Rep. Memor., 1155 (1928).
5. Frazer, R. A., and Duncan, W. J., A.R.C. Rep. Memor., 1255 (1931).