• Thanks to those who poked holes in our story on the space-faring surgery robot (5 April, p 10): we should have said the machine would repair perforated ulcers, not perforate them.
• We made an accidental precedent claim in our leader on gravitational waves (12 April, p 5). As the accompanying feature noted (p 38), the BICEP2 results provide new indirect evidence of their existence, but not the first.
• It was Peter Rhee, not Hasan Alam, who first demonstrated the technique of emergency preservation and resuscitation in pigs (29 March, p 8).
