Abstract :
Figure 2 in Shimon Ullman\´s "Analysis of Visual Motion by Biological and Computer Systems" was incorrectly referenced as Figure 2a in the text of the article. The end of the paragraph containing the figure reference (August 1981 Computer, p. 59) should have read as follows: "The organization of an on-center cell is shown in Figure 2. The response is maximal in the middle of the receptive field, decreases as the light stimulus is moved outward, and becomes negative in the surround." That is, the sentence referring to Figure 2b, not used in the article, should have been deleted.
