The statement required in (b) above must be signed by the person who delivered the subpoena, and must show that the person who served the subpoena was authorized to do so. The authorization comes from Rules 176.5(a) and 500.8(d), which specify the manner of service and the persons who may make service. A person need not be an authorized process server in order to serve a subpoena. Therefore, the requirement that the proof of service must be either verified or signed under penalty of perjury does not apply to proof of service of a subpoena. The proof of service should reflect that the person making service is either a sheriff or constable of the State of Texas, or is a person who is not a party and is 18 years of age or older. If the process server is certified by the Supreme Court, the process server should include his or her certification number and expiration date even though these items are not expressly required by the rules for subpoenas.