• Jonathan Marks did not conduct research at the Hoover Institution, contrary to our report (10 February, p 13). He has seen a copy of documents archived at the institution. The documents are not classified but they will not be open for public inspection until 2010.
• The story “Air rescue comes to Everest” (17 February, p 23) was truncated in a production error. It should conclude: “The helicopter will begin trial flights in the Himalayas in January 2008.”
• In the article on “unnatural selection” (17 February, p 6) we accidentally added an “e” to Christian Roberge’s first name.
