Bobet, A., and Einstein, H.H. (1997). Mechanized tunneling in squeezing ground – From basic thoughts to continuous tunneling. In Tunnels for people: proceedings of World Tunnel Congress ’97 (J. Golser, W.H., Hinkel, W. Schubert, eds.), 23rd General Assembly of the International Tunneling Association, 12-17 April 1997, Vienna, Austria, pp. 619-632. Balkema, Rotterdam. ISBN 9789054108689