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Syntax Definition wsb 1648
Description: Extend wff definition to include proper substitution (read "the wff that results when is properly substituted for in wff "). (Contributed by NM, 24-Jan-2006.)
Hypotheses
Ref Expression
wph
vx
vy
Assertion
Ref Expression
wsb
See definition df-sb 1649 for more information.
Colors of variables: wff setvar class
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