reserve E for compact non vertical non horizontal Subset of TOP-REAL 2,
  C for compact connected non vertical non horizontal Subset of TOP-REAL 2,
  G for Go-board,
  i, j, m, n for Nat,
  p for Point of TOP-REAL 2;

theorem
  for f being FinSequence holds f is empty iff Rev f is empty
proof
  let f be FinSequence;
  thus f is empty implies Rev f is empty;
  assume Rev f is empty;
  then reconsider g=Rev f as empty FinSequence;
  Rev g is empty;
  hence thesis;
end;
