public function getStartDate()
    {
        $topic = BaseManager::build('FelixOnline\Core\Topic', 'article_topic', 'topic')
            ->filter('topic = "%s"', array($this->getSlug()));

        $article = BaseManager::build('FelixOnline\Core\Article', 'article', 'id')
            ->join($topic, 'LEFT', 'id', 'article')
            ->filter('published > 0')
            ->order('published', 'ASC')
            ->limit(0, 1)
            ->values();

        if (!$article) {
            throw new \FelixOnline\Exceptions\InternalException('No articles posted in this topic');
        }

        return($article[0]->getPublished());
    }