References
- Op. cit., pp. 28–29.
- Op. cit., pp. 56–57.
- The example is taken from Scherkenbach, 1988, p. 27, according to which many people see three Fs, many see six Fs, while a few see two, four, five or seven Fs.
- See more about this in J. J. Dahlgaard & O. Skyum, 1988, p. 101.