S.D. Codified Laws § 5-18A-20

Brand name specification may be used only if the purchasing agency makes a written determination that only the identified brand name item or items will satisfy the agency's needs. The agency shall seek to identify sources from which the designated brand name item or items can be obtained and shall solicit such sources to achieve whatever degree of price competition is practicable. If only one source can supply the requirement, the procurement shall be made under the sole source procurement provisions of § 5-18A-8.