private function getArticleForPage(ArticleDocument $article, $pageNumber)
    {
        $children = $article->getChildren();
        if (null === $children || 1 === $pageNumber) {
            return $article;
        }

        foreach ($children as $child) {
            if ($child instanceof ArticlePageDocument && $child->getPageNumber() === $pageNumber) {
                return $child;
            }
        }

        return $article;
    }