[1]
Mann, L.M. et al. 1918. 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, (Nov. 1918), 140–149. DOI:https://doi.org/10.9750/PSAS.052.140.149.