54 STAT.] 76TH CONG., 3D SESS.-CH. 722-SEPT. 18 , 1940 as may be required by the Commission under paragraph (1) hereof, shall also be under oath whenever the Commission so requires. "(3) The Commission may, in its discretion, for the purpose of enabling it the better to carry out the purposes of this part, prescribe a uniform system of accounts applicable to any class of carriers subject thereto, and a period of time within which such class shall have such uniform system of accounts, and the manner in which such accounts shall be kept. "(4) The Commission shall, as soon as practicable, prescribe for carriers the classes of property for which depreciation charges may properly be included under operating expenses, and the rate or rates of depreciation which shall be charged with respect to each of such classes of property, classifying the carriers as it may deem proper for this purpose. The Commission may, when it deems necessary, modify the classes and rates so prescribed. When the Commission shall have exercised its authority under the foregoing provisions of this paragraph, carriers shall not charge to operating expenses any depreciation charges on classes of property other than those prescribed by the Commission, or charge with respect to any class of property a rate of depreciation other than that prescribed therefor by the Com- mission, and no such carrier shall include under operating expenses any depreciation charge in any form whatsoever other tan as pre- scribed by the Commission. "(5) The Commission may, in its discretion, prescribe the forms of any and all accounts, records, and memoranda to be kept by carriers and their lessors, including the accounts, records, and memoranda of the movement of traffic, as well as of the receipts and expenditures of moneys, and it shall be unlawful for such carriers or lessors to keep any accounts, records, and memoranda contrary to any rules regula- tions, or orders of the Commission with respect thereto. The Com- mission or any duly authorized special agent, accountant, or examiner thereof shall at all times have authority to inspect and copy any and all accounts, books, records, memoranda, correspondence, and other documents, of such carriers and lessors, and such accounts, books, records, memoranda, correspondence, and other documents, of any person controlling, controlled by, or under common control with any such carrier, as the Commission deems relevant to such person's rela- tion to or transactions with such carrier. The Commission or its duly authorized special agents accountants. or examiners shall at all times have access to all lands, buildings, or equipment of such carriers or lessors, and shall have authority under its order to inspect and exam- ine any and all such lands, buildings, and equipment. Such carriers, lessors, and other persons shall submit their accounts, books, records, memoranda, correspondence, and other documents for the inspection and copying authorized by this paragraph, and such carriers and lessors shall submit their lands, buildings, and equipment to inspection and examination, to any duly authorized special agent, accountant, or examiner of the Commission, upon demanand and the display of proper credentials. "(6) The Commission or any duly authorized special agent, account- ant, or examiner thereof shall at all times have authority to inspect and copy any and all accounts, books, records, memoranda, correspond- ence , and other documents, of persons which furnish cars or protective service against heat or cold to or on behalf of any carrier by railroad or express company subject to this part: Provided,however, That such authority shall be limited to accounts, books, records, memoranda, correspondence, or other documents which pertain or relate to the cars or protective service so furnished. The Commission shall further have authority, in its discretion, to prescribe the forms of any or al accounts, records, and memoranda which it is authorized by this Uniform system of accounts. Depreciation charges; rates. Modifications. Forms of accounts, records, and memo- randa. Inspection and ex- amination ofaccounts, lands, equipment, etc. Inspection of ac- counts on heat and cold service. Proviso. Authority limited. Forms.