Some definitions of interest.
comment	Def  Kind of comment: $kind == a
exteq	Def  A =ext B == (x:A. x  B) & (x:B. x  A)
int_seg	Def  {i..j} == {k:| i  k < j }
	Thm*  m,n:. {m..n}  Type
singleton	Def  {a:T} == {x:T| x = a  T }
	Thm*  T:Type, a:T. {a:T}  Type

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