1. Uehigashi, K., Tokairin, Y., Ishikawa, K., Kikuchi, T.: Possibility of rock excavation by boom-type tunneling machines. In: 6th Australian Tunneling Conference, Melbourne 1987, pp. 253–259
2. Day, M., Goudie, A.: Field assessment of rock hardness using the Schmidt test hammer. Geomorph. Res. Group Technol. Bull. 18, 19–29 (1977)
3. Day, M.J.: Rock hardness: field assessment and geomorphic importance. Prof. Geograph. 32(1), 72–81 (1980)
4. Matthews, J.A., Shakesby, R.A.: The status of the ‘Little Ice Age’ in southern Norway: relative-age dating of Neoglacial moraines with Schmidt hammer and lichenometry. Boreas 13(3), 333–346 (1984)
5. McCarroll, D.: The Schmidt hammer as a measure of degree of rock surface weathering and terrain age. Dating in exposed and surface contexts, 29–45 (1994)