1. Arioğlu, E., Tokgoz, N. 1991. Estimation of rock strength: rapidly and reliably by the Schmidt hammer. J. Mines, Metals Fuels, September–October: pp. 327–330.
2. Ayaydin, N. 1994. Metro Istanbul. World Tunneling, April, pp. 113–114.
3. Ayday, C., Goktan, R.M. 1992. Correlations between L and N-type Schmidt hammer rebound values obtained during field testing. Proceedings, Eurock, pp. 47–49.
4. Bilgin, N., Seyrek. T., Shahriar, K. 1988. Roadheader performance in Istanbul, Golden Horn clean up contributes valuable data. Tunnels and Tunneling, June: pp. 41–44.