The commissioner shall prescribe the books and the forms of accounts to be kept by the holders of certificates under this article, which books and accounts shall be preserved for such reasonable time as may be prescribed by the commissioner. The books and records of every certificate holder shall be at all times open to the inspection of the commissioner or any agent of the department for such purpose. The commissioner shall have the power to examine the books and records of all motor carriers to whom he or she has granted certificates or permits to operate under this article and to examine under oath the officers and agents of any motor carrier with respect thereto.