“Such annual report shall be kept on file with the superintendent and at the principal office of the trustees. The report, or such portion thereof as the superintendent deems appropriate, shall be made available by the superintendent or by the trustees, or both, for inspection by any employer contributing to such fund, by any labor organization which is a party to an agreement establishing such fund, or by any employee covered by such fund. In addition and to such extent that he deems it to be in the public interest, the superintendent may require the trustees to mail such report or such portions of it to any or all of such parties.”