There were two studies in 1980, and the information can be found in the
following books:
* Radl. "Ergonomic Aspects of Visual Display Terminals"; London Taylor and
Francis, 1980.
* Bauer and Cavonius. "Improving the Legibility of Visual Display Units through
Contrast Reversal"; 1980.
There is also a newer book that summarizes the information in the other two
books:
* Etienne Grandjean. "Ergonomics in Computerized Offices"; 1987.