• In our piece “Bones tell where victims lived and when they died” (15 March, p 7), we should have mentioned that Benjamin Swift, of the Department of Pathology at the University of Leicester, came up with the idea of using lead and polonium ratios to date bones. He collaborated with Stuart Black to test the technique.
• An error crept in during the editing of our feature on missing baryonic matter (22 March, p 40). We stated that oxygen atoms shake off five or six of their eight electrons to leave O2+ and O3+ ions when we should have said O5+ and O6+.
Following our story about patterns of email traffic (29 March, p 19), we heard that Roger Guimerá of Rovira i Virgili University in Tarragona, Spain, and his colleagues reported similar results last year. Details are at .
