public function &GetArticleGroups()
    {
        $oArticleGroups = &$this->GetFromInternalCache('oArticleGroups');
        if (is_null($oArticleGroups)) {
            $oArticleGroups = &TdbShopArticleGroupList::GetArticleGroups($this->id);
            $this->SetInternalCache('oArticleGroups', $oArticleGroups);
        }

        return $oArticleGroups;
    }