
theorem Th03:
  for I be Subset of REAL st I is Interval holds I in Borel_Sets
proof
  let I be Subset of REAL;
  assume I is Interval; then
  I is open_interval or I is closed_interval or
  I is right_open_interval or I is left_open_interval by MEASURE5:1;
  hence thesis by Lm01,Lm02,Lm03,Lm04;
end;
