reserve T for TopSpace;
reserve T for non empty TopSpace;
reserve F for Subset-Family of T;

theorem
  union(Int Cl Int F) c= Int Cl Int(union F)
proof
A1: Int(union Cl Int F) c= Int Cl Int(union F) by Th48,TOPS_1:19;
  union(Int Cl Int F) c= Int(union Cl Int F) by Th27;
  hence thesis by A1;
end;
