private function getOpenGraph(): array {
        $results = array();

        $nodes = $this->article()->getDoc()->find('meta[property^="og:"]');

        foreach ($nodes as $node) {
            $property = explode(':', $node->attr('property'));
            array_shift($property);
            $results[implode(':', $property)] = $node->attr('content');
        }

        // Additionally retrieve type values based on provided og:type (http://ogp.me/#types)
        if (isset($results['type'])) {
            $nodes = $this->article()->getDoc()->find('meta[property^="' . $results['type'] .':"]');

            foreach ($nodes as $node) {
                $property = explode(':', $node->attr('property'));
                array_shift($property);
                $results[implode(':', $property)] = $node->attr('content');
            }
        }

        return $results;
    }