Simpson, W Douglas. “Notes on Lulach’s Stone, Kildrummy, Aberdeenshire; a Symbol Stone Recently Found in Mortlach Churchyard, Banffshire; And Other Antiquities”. Proceedings of the Society of Antiquaries of Scotland 60 (November 30, 1926): 273–280. Accessed May 1, 2024. https://journals.socantscot.org/index.php/psas/article/view/7676.