public function toArray()
    {
        return [
            'title'         => $this->title,
            'description'   => $this->description,
            'content'       => $this->content,
            'authors'       => array_map(function ($author) {
                                            return $author->toArray();
                                        }, isset($this->authors) ? $this->authors : []),
            'date'          => $this->date,
            'permalink'     => $this->permalink,
        ];
    }