For The Record

摘要

1. The Crab nebula is in the constellation of Taurus not, as we stated, Orion (7 March, p 14).rn2. The materials used to print 3D images of bones are tricalcium phosphate and poly(lactic-co-glycolic acid), not tri-calcium triphosphate and polylactic acid (7 March, p 13).rn3. In "Surviving in a warmer world" (28 February, p 28) we said thatrn"9 million people would need 18,000 square kilometres of land to live on". 4. That figure should, of course, have been 9 billion people, and the area of land 180,000 square kilometres.