Smith, John Alexander. “Notes of Small Ornamented Stone Balls Found in Different Parts of Scotland, &C., With Remarks on Their Supposed Age and Use”. Proceedings of the Society of Antiquaries of Scotland 11 (November 30, 1875): 29–62. Accessed April 25, 2024. https://journals.socantscot.org/index.php/psas/article/view/5729.