theorem
  ex f be Function of [:TopSpaceMetr Euclid i,TopSpaceMetr Euclid j:],
    TopSpaceMetr Euclid (i+j) st f is being_homeomorphism &
  for fi,fj be FinSequence st [fi,fj] in dom f holds f.(fi,fj) = fi^fj by Lm2;
