Theorem bj-nfsab1

Description: Remove dependency on ax-13 from nfsab1 . UPDATE / TODO: nfsab1 does not use ax-13 either anymore; bj-nfsab1 is shorter than nfsab1 but uses ax-12 . (Contributed by BJ, 23-Jun-2019) (Proof modification is discouraged.)

	Ref	Expression
Assertion	bj-nfsab1	$$⊢Ⅎxy\in \left\{x|\phi \right\}$$

Proof

Step	Hyp	Ref	Expression
1		hbab1	$$⊢y\in \left\{x|\phi \right\}\to \forall xy\in \left\{x|\phi \right\}$$
2	1	nf5i	$$⊢Ⅎxy\in \left\{x|\phi \right\}$$