theorem Th4:
  the carrier of TOP-REAL n = the carrier of REAL-NS n
  proof
    thus the carrier of TOP-REAL n
    = the carrier of the RLSStruct of (TOP-REAL n)
    .= the carrier of the RLSStruct of REAL-NS n by Th1
    .= the carrier of REAL-NS n;
  end;
