public function extract($dom, $url)
    {
        $this->resetUrls();
        $crawler = new DomCrawler($dom, $url);
        $links = $crawler->filter('body a')->links();

        foreach ($links as $link) {
            if (!in_array($link->getUri(), $this->urls)) {
                $this->urls[] = $link->getUri();
            }
        }

        return $this->urls;
    }