Europe SGS-Forestry and the Soil Association. They were subsequently joined by SKAL (from the Netherlands) and the "Institut fr Marktkologie" (from Switzerland). The kind of certification promoted by the FSC is called product or performance certification. It involves careful tracking of logs and wood products over a chain of custody through its entire processing. It is far more complex than, say, certification of organic foods, because of the number of suppliers, contractors, processors, assemblers and retailers involved. Sustainably harvested wood products require either separate product streams in mills that are audited as part of the third-party certification process, or special tagging of certified material as it moves through the mill alongside uncertified stock (Wilson & Malin, 1997b).