(50)In view of the detrimental effects on competition, negotiated procedures without prior publication of a contract notice should be used only in very exceptional circumstances. This exception should be limited to cases where publication is either not possible, for reasons of extreme urgency brought about by events unforeseeable for and not attributable to the contracting authority, or where it is clear from the outset that publication would not trigger more competition or better procurement outcomes, not least because there is objectively only one economic operator that can perform the contract. This is the case for works of art, where the identity of the artist intrinsically determines the unique character and value of the art object itself. Exclusivity can also arise from other reasons, but only situations of objective exclusivity can justify the use of the negotiated procedure without publication, where the situation of exclusivity has not been created by the contracting authority itself with a view to the future procurement procedure. Contracting authorities relying on this exception should provide reasons why there are no reasonable alternatives or substitutes such as using alternative distribution channels including outside the Member State of the contracting authority or considering functionally comparable works, supplies and services. Where the situation of exclusivity is due to technical reasons, they should be rigorously defined and justified on a case-by-case basis. They could include, for instance, near technical impossibility for another economic operator to achieve the required performance or the necessity to use specific know-how, tools or means which only one economic operator has at its disposal. Technical reasons may also derive from specific interoperability requirements which must be fulfilled in order to ensure the functioning of the works, supplies or services to be procured. Finally, a procurement procedure is not useful where supplies are purchased directly on a commodity market, including trading platforms for commodities such as agricultural products, raw materials and energy exchanges, where the regulated and supervised multilateral trading structure naturally guarantees market prices.