@article{Mann_Scott_Petrie_1918, title={The Prehistoric and Early Use of Pitchstone and Obsidian}, volume={52}, url={http://journals.socantscot.org/index.php/psas/article/view/7425}, DOI={10.9750/PSAS.052.140.149}, journal={Proceedings of the Society of Antiquaries of Scotland}, author={Mann, Ludovic and Scott, A and Petrie, W M}, year={1918}, month={Nov.}, pages={140-149} }