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Metamath Proof Explorer

Theorem nnssz

Description: Positive integers are a subset of integers. (Contributed by NM, 9-Jan-2002)

		Ref	Expression
	Assertion	nnssz	$⊢ ℕ \subseteq ℤ$

Step	Hyp	Ref	Expression
1		nnz	$⊢ x \in ℕ \to x \in ℤ$
2	1	ssriv	$⊢ ℕ \subseteq ℤ$