Each party may submit to the Commission on or before a date specified in the notice of investigation issued pursuant to § 207.12 a written brief containing information and arguments pertinent to the subject matter of the investigation. Briefs shall be signed, shall include a table of contents, and shall contain no more than fifty (50) pages of textual material. Any person not a party may submit a brief written statement of information pertinent to the investigation within the time specified and the same manner specified for the filing of briefs. In addition, the presiding official may permit persons to file within a specified time answers to questions or requests made by the Commission's staff. If the presiding official deems it appropriate, the presiding official shall hold a conference. The conference, if any, shall be held in accordance with the procedures in § 201.13 of this chapter, except that in connection with its presentation a party may provide written witness testimony at the conference. The party shall file the written testimony in accordance with § 201.8(d) of this chapter no later than the date of the conference. If the written testimony is filed on the day of the conference, the party shall also file with the Secretary on that day nine (9) true paper copies of any such written testimony. The presiding official may request the appearance of witnesses, take testimony, and administer oaths.