scheme :: YELLOW_9:sch 3
FraenkelComplement2{ F₁() -> non empty RelStr , F₂() -> Subset-Family of F₁(), F₃() -> set , F₄( set ) -> Subset of F₁() } :

COMPLEMENT F₂() = { F₄(a) where a is Element of F₁() : a in F₃() }

provided

A1: F₂() = { (F₄(a) `) where a is Element of F₁() : a in F₃() }