• MiG-29 aircraft have fixed wings, contrary to what we said on 13 December 2003, p 28. We could have referred to the MiG-23 or MiG-27 as examples of variable-geometry planes.
• Letter writer Samuel Thomas would like to clarify that he is still an undergraduate student of chemistry at King’s College London (20 December 2003, p 34). The course is being phased out over the next three years.
