protected function _get_domain( $content ) {
		$permalink = $this->get_permalink();
		if ( ! $permalink ) {
			$permalink = $this->_get_permalink( $content );
		}

		preg_match( '/https?:\/\/([^\/]+)/', $permalink, $reg );
		if ( ! empty( $reg[1] ) ) {
			return $reg[1];
		}
	}