Metamath Proof Explorer

Theorem impexp

Description: Import-export theorem. Part of Theorem *4.87 of WhiteheadRussell p. 122. (Contributed by NM, 10-Jan-1993) (Proof shortened by Wolf Lammen, 24-Mar-2013)

Ref Expression
Assertion impexp φ ψ χ φ ψ χ


Step Hyp Ref Expression
1 pm3.3 φ ψ χ φ ψ χ
2 pm3.31 φ ψ χ φ ψ χ
3 1 2 impbii φ ψ χ φ ψ χ