In "Grant Wood at the Smithsonian" (Plus, Mar. 13), we mistakenly said American Gothic would not be part of the Grant Wood exhibition running through July 16 at the Smithsonian American Art Museum. The painting, on loan from the Art Institute of Chicago, will be in Washington through June 11. "Filtering out the madness before a transfusion" (Developments to Watch, Mar. 6) on mad cow disease should have clarified that Pall Corp.'s (PLL
) device for filtering prions from blood is already available in Europe. In "The struggle to measure performance" (News: Analysis & Commentary, Jan. 9), a source line in the table "Performance Art" attributing some of the content to Hewitt Associates was inadvertently omitted.