For the purpose of all hearings and investigations, which, in the opinion of the Board, are necessary and proper for the exercise of the powers vested in it by sections 159 and 160 of this title—

((1)) ** Documentary evidence; summoning witnesses and taking testimony** The Board, or its duly authorized agents or agencies, shall at all reasonable times have access to, for the purpose of examination, and the right to copy any evidence of any person being investigated or proceeded against that relates to any matter under investigation or in question. The Board, or any member thereof, shall upon application of any party to such proceedings, forthwith issue to such party subpenas requiring the attendance and testimony of witnesses or the production of any evidence in such proceedings or investigation requested in such application. Within five days after the service of a subpena on any person requiring the production of any evidence in his possession or under his control, such person may petition the Board to revoke, and the Board shall revoke, such subpena if in its opinion the evidence whose production is required does not relate to any matter under investigation, or any matter in question in such proceedings, or if in its opinion such subpena does not describe with sufficient particularity the evidence whose production is required. Any member of the Board, or any agent or agency designated by the Board for such purposes, may administer oaths and affirmations, examine witnesses, and receive evidence. Such attendance of witnesses and the production of such evidence may be required from any place in the United States or any Territory or possession thereof, at any designated place of hearing.

((2)) ** Court aid in compelling production of evidence and attendance of witnesses** In case of contumacy or refusal to obey a subpena issued to any person, any district court of the United States or the United States courts of any Territory or possession, within the jurisdiction of which the inquiry is carried on or within the jurisdiction of which said person guilty of contumacy or refusal to obey is found or resides or transacts business, upon application by the Board shall have jurisdiction to issue to such person an order requiring such person to appear before the Board, its member, agent, or agency, there to produce evidence if so ordered, or there to give testimony touching the matter under investigation or in question; and any failure to obey such order of the court may be punished by said court as a contempt thereof.

((3)) ** Repealed. , , **

((4)) ** Process, service and return; fees of witnesses** Complaints, orders, and other process and papers of the Board, its member, agent, or agency, may be served either personally or by registered or certified mail or by telegraph or by leaving a copy thereof at the principal office or place of business of the person required to be served. The verified return by the individual so serving the same setting forth the manner of such service shall be proof of the same, and the return post office receipt or telegraph receipt therefor when registered or certified and mailed or when telegraphed as aforesaid shall be proof of service of the same. Witnesses summoned before the Board, its member, agent, or agency, shall be paid the same fees and mileage that are paid witnesses in the courts of the United States, and witnesses whose depositions are taken and the persons taking the same shall severally be entitled to the same fees as are paid for like services in the courts of the United States.

((5)) ** Process, where served** All process of any court to which application may be made under this subchapter may be served in the judicial district wherein the defendant or other person required to be served resides or may be found.

((6)) ** Information and assistance from departments** The several departments and agencies of the Government, when directed by the President, shall furnish the Board, upon its request, all records, papers, and information in their possession relating to any matter before the Board.