7 U.S. Code § 4811 - Referendum
For the purpose of determining whether an order then  effect shall be continued during the period beginning not earlier than 24 months after the issuance of the order and ending not later than 30 months after the issuance of the order, the Secretary shall conduct a referendum among persons who have been pork producers and importers during a representative period, as determined by the Secretary.
A referendum shall be conducted in such manner as prescribed by the Secretary.
A referendum to amend the initial order shall be conducted pursuant to this section.
 So in original. Probably should be followed by “in”.