The commission shall cause all of its records including, but not limited to, minutes or transcripts, reports, studies, forms of instruments, bidding papers, notices, advertisements, invitation for bids, bids, executed instruments, and correspondence to be kept and maintained permanently. Such records shall be open to public inspection and may be inspected by any citizen of the state during usual business hours unless the same are being used by the commission or by its employees in the performance of its or their duties in reference thereto.