Section 13.111 - Subpoenas(a) At the discretion of the presiding officer, or at the request of a party to the investigation, the presiding officer may issue a subpoena directing any person to appear at a designated time and place to testify or to produce documentary or physical evidence relating to any matter under investigation.(b) Subpoenas must be served by personal service on the person or an agent designated in writing for the purpose, or by registered or certified mail addressed to the person or agent. Whenever service is made by registered or certified mail, the date of mailing will be considered the time when service is made.(c) Subpoenas extend in jurisdiction throughout the United States and any territory or possession thereof.