Some definitions of interest.
int_lower	Def {...i} == {j:| ji }
	Thm* i:. {...i}  Type
nat	Def  == {i:| 0i }
	Thm*   Type
le	Def AB == B<A
	Thm* i,j:. (ij)  Prop
nat_plus	Def  == {i:| 0<i }
	Thm*   Type

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