Some definitions of interest.
nat	Def  == {i:| 0i }
	Thm*   Type
nequal	Def a  b  T == a = b  T
	Thm* A:Type, x,y:A. (x  y)  Prop
sfa_doc_exteq	Def A =ext B == (X:A. X  B) & (X:B. X  A)

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