• In our story about North Korea’s nuclear test (14 October, p 9) the size of the explosion, estimated at 0.5 kilotons, or the equivalent of 500 tons of TNT, is incorrectly compared to the Oklahoma City bomb of 1995. In fact, the Oklahoma City bomb was smaller by a factor of around 100.
• In the feature “Legally high” (30 September, p 41) we erroneously referred to John Halpern of Harvard Medical School as a psychologist. He is a psychiatrist.
