Phillips, R. J. (1979). Making maps easy to read - A summary of research. In A. Kolers, M. E. Wrolstad & H. Bouma, Processing of Visible Language (vol. 1). New York: Plenum Press.

Poorly designed maps can seriously reduce the efficiency of the map reader and lead to mistakes which are inconvenient, costly, or even dangerous. Experimental studies of map legibility are beginning to provide the map designer with objective information on topics such as colour coding, relief portrayal, and lettering. Two research groups are active in the United Kingdom and a number elsewhere, particularly in the United States. As testing methods improve, there is a good possibility that designers may be persuaded to use tests themselves to compare alternative map designs.