Perspective. In the article “Active galactic nuclei” by Andrew Fabian, which appeared in number 9, April 27, 1999, of Proc. Natl. Acad. Sci. USA (96, 4749–4751), the following statement was omitted from the legend to Fig. 1: “Fig. 1 was reprinted with permission from ref. 18 (Copyright 1997, Mon. Not. R. Astron. Soc.).”