reserve T for TopStruct;
reserve GX for TopSpace;

theorem Th11:
  for X9 being SubSpace of T, A being Subset of X9 holds A is Subset of T
proof
  let X9 be SubSpace of T, A be Subset of X9;
  [#]X9 c= [#]T by Def4;
  hence thesis by XBOOLE_1:1;
end;
