In view of the factual contentions advanced in the petition for rehearing filed by the petitioner and in the respondent's reply thereto, the petition for rehearing is granted and the order heretofore entered, 371 U.S. 531, 83 S.Ct. 403, 9 L.Ed.2d 486, dismissing the writ of certiorari is vacated. The judgment of the Court of Appeals, 111 U.S.App.D.C. 294, 296 F.2d 416, is vacated and the cause is remanded to the District Court with instructions to hold a hearing and determine whether the petitioner, desiring the presence of witnesses at his hearing, either discharged his initial burden under the applicable regulations by making timely and sufficient attempt to obtain their presence or, under the circumstances and without fault of his own, was justified in failing to make such attempt, and, if so, whether proper and timely demand was made upon the Air Force so that it was required to produce such witnesses for cross-examination. Upon making such determination, the District Court shall thereupon enter such further order or judgment as may be appropriate.