1. Barla, G., Pelizza, S., 2000. TBM tunneling in difficult ground conditions. In: GeoEng2000 – An International Conference on Geotechnical & Geological Engineering, Melbourne, Australia, 20pp.
2. Blindheim, O.T., Grøv, E., Nilsen, B., 2002. The effect of mixed face conditions (MFC) on hard rock TBM performance. In: ITA World Tunnel Congress, Sydney.
3. Code of Practice for Site Investigations, BS 5930: 1999;British Standards Institution,1999
4. Centis, S., Giacomin, G., 2004. EPB tunneling in highly variable ground – the experience of Oporto Light Metro. Underground space for sustainable urban development. In: Proceedings of the 30th ITA-AITES World Tunnel Congress, Singaproe, vol. 1, pp. 387–394.
5. Della Valle, N., 2001. Boring through a rock-soil interface in Singapore. In: Proceedings of the Rapid Excavation and Tunnelling Conference, pp. 633–645.