reserve n,m for Nat,
  r,r1,r2,s,t for Real,
  x,y for set;

theorem
  for D,C be non empty set, F be PartFunc of D,REAL, G be PartFunc of C,
  REAL holds F,G are_fiberwise_equipotent iff -F, -G are_fiberwise_equipotent
by Th11;
