private static function createArticles(Collection $items) : Collection
    {
        return $items->map(function ($item) {
            return Article::create($item);
        })->filter()->sort(function ($first, $second) {
            if ($first->timestamp === $second->timestamp) {
                return strnatcmp($first->title, $second->title);
            } else {
                return $first->timestamp < $second->timestamp ? -1 : 1;
            }
        })->map(function (Article $article, $key) {
            $article->setId($key);
            return $article;
        });
    }