Some definitions of interest.
anti_sym	Def AntiSym(T;x,y.R(x;y)) == x,y:T. R(x;y)  R(y;x)  x = y
	Thm* T:Type, R:(TTProp). AntiSym(T;x,y.R(x,y))  Prop
iff	Def P  Q == (P  Q) & (P  Q)
	Thm* A,B:Prop. (A  B)  Prop

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