Some definitions of interest.
divides	Def b | a == c:. a = bc
	Thm* a,b:. (a | b)  Prop
iff	Def P  Q == (P  Q) & (P  Q)
	Thm* A,B:Prop. (A  B)  Prop
int_nzero	Def  == {i:| i  0 }
	Thm*   Type

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