References
- Chapanis , A. , Garner , W. R. and Morgan , C. T. 1949 . Applied Experimental Psychology , New York : John Wiley and Sons .
- Duke-Elder , W. S. 1942 . Text-Book of Ophthalmology , London : Henry Kimpton .
- Lawson , R. W. 1948 . Blinking: its role in physical measurement . Nature , 161 : 154 – 157 .
- Lawson , R. W. 1948 . Photographic evaluation of blackout indices . Nature , 162 : 531 – 532 .