(a) The first claim for compensation for an injury shall be filed in writing within sixty days after the injury on forms to be furnished by the Administrator. Such claims shall be filed at the office of the Administrator or deposited in the mail properly stamped and addressed to the Administrator or to any person whom the Administrator may designate. Each claim shall be sworn to by the injured person or whoever acts in his behalf, and shall be accompanied by a doctor's certificate stating the nature and probable extent of the disability, or by a death certificate.
(b) Supplementary claims, if any, for protracted disability or for any additional compensation claimed, shall be filed in the manner directed by the Administrator.
(c) For good and reasonable cause shown, the Administrator may extend the time limit set by this section.