for D being set
for p1, p2 being FinSequence of D st p1 is one-to-one & p2 is one-to-one & rng p1 = rng p2 holds
( dom p1 = dom p2 & ex P being Permutation of (dom p1) st
( p2 = p1 * P & dom P = dom p1 & rng P = dom p1 ) )