Some definitions of interest.
nat	Def   == {i:| 0i }
	Thm*    Type
nat_to_nat_pair	Def  nat_to_nat_pair(i) == next_nat_pair{i}(<0,0>)
	Thm*  nat_to_nat_pair
not	Def  A == A  False
	Thm*  A:Prop. (A)  Prop

About: IF YOU CAN SEE THIS go to /sfa/Nuprl/Shared/Xindentation_hack_doc.html