reserve TS for 1-sorted,
  K, Q for Subset of TS;
reserve TS for TopSpace,
  GX for TopStruct,
  x for set,
  P, Q for Subset of TS,
  K , L for Subset of TS,
  R, S for Subset of GX,
  T, W for Subset of GX;

theorem Th15:
  Int([#] TS) = [#] TS
proof
  Int ([#] TS) = ({} TS)` by PRE_TOPC:22;
  hence thesis;
end;
