(a) Witnesses shall be examined orally under oath except that for good and exceptional cause the administrative law judge may permit their testimony to be taken by deposition under oath.

(b) The administrative law judge shall upon application by any party, and upon a showing of general relevance and reasonable scope of the evidence sought, issue subpoenas requiring the attendance and testimony of witnesses and the production of evidence under oath, including books, records, correspondence, or documents. Applications for the issuance of subpoenas duces tecum shall specify the books, records, correspondence or other documents sought.

(c) Witnesses summoned before the administrative law judge 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. Witness fees and mileage shall be paid by the party at whose instance the witnesses appear, and the person taking the depositions shall be paid by the party at whose instance the depositions are taken.