1. Bamford, W. F. 1984. Rock test indices are being successfully correlated with tunnel boring machine performance. Proceedings of the 5th Australian Tunneling Conference, Melbourne, Australian, 9–22.
2. Barla, G., and L. Vai. 1999. Indagini geotecniche per la caratterizzazione del sottosuolo di Torino lungo il tracciato del Passante Ferroviario. Proceedings of the 20th Congresso Nazionale di Geotecnica, (CNG’ 99), Parma, Italy, 335–42.
3. Bieniawski, Z. T., B. Celada, J. M. Galera, and I. Tardáguila. 2008. New applications of the excavability index for selection of TBM types and predicting their performance. Proceedings of the ITA-AITES World Tunnel Congress & 34th ITA General Assembly, Agra, India.