Mann, Ludovic McLellan, A Scott, and W M Flinders Petrie. “The Prehistoric and Early Use of Pitchstone and Obsidian: With Report on Petrology; And a Note of Egyptian and Aegean Discoveries”. Proceedings of the Society of Antiquaries of Scotland 52 (November 30, 1918): 140–149. Accessed November 22, 2024. https://journals.socantscot.org/index.php/psas/article/view/7425.