theorem
  for V being Abelian add-associative right_zeroed right_complementable
  non empty addLoopStr, v,u,w being Element of V holds
  Sum<* u,v,w *> = Sum<* w,v,u *>
proof
  let V be Abelian add-associative right_zeroed right_complementable non
  empty addLoopStr, v,u,w be Element of V;
  thus Sum<* u,v,w *> = Sum<* w,u,v *> by Th68
    .= Sum<* w,v,u *> by Th66;
