Theorem ss2abiOLD

Description: Obsolete version of ss2abi as of 28-Jun-2024. (Contributed by NM, 31-Mar-1995) (Proof modification is discouraged.) (New usage is discouraged.)

	Ref	Expression
Hypothesis	ss2abiOLD.1	|- ( ph -> ps )
Assertion	ss2abiOLD	|- { x | ph } C_ { x | ps }

Proof

Step	Hyp	Ref	Expression
1		ss2abiOLD.1	|- ( ph -> ps )
2		ss2ab	|- ( { x | ph } C_ { x | ps } <-> A. x ( ph -> ps ) )
3	2 1	mpgbir	|- { x | ph } C_ { x | ps }