IF YOU CAN SEE THIS go to /sfa/Nuprl/Shared/Xindentation_hack_doc.html
At:
nat to nat pair surj111 1. k : 2. k1:. k1<k (x,y:. x+y = k1 (a:. nat_to_nat_pair(a) = <x,y>))
3. x : 4. x1:. x1<x (y:. x1+y = k (a:. nat_to_nat_pair(a) = <x1,y>))
5. y : 6. x+y = k a:. nat_to_nat_pair(a) = <x,y>