Every original work of an artist must be contrasted, and a certificate of authenticity must be available in order to always have the peace of mind that, not only is it an original work, but that the artist was involved in such work, which are not remnants or stock of any company for which the author is not responsible.
Whether you buy it from the artist himself in his gallery, workshop or from an authorized distributor you must have his certificate of authenticity available and you can demand it.
To see the official distributors you can visit the section dedicated to it on the web: