"National Research Council (U.S.). Highway Research Board." . . "Excavation and tunneling." . . "Tunnel supports." . . . . . . . . . . . "Symposium: Rapid Excavation : 5 reports ; [papers sponsored by Committee on Soil and Rock Properties and presented at the 49th annual meeting of the Highway Research Board]" . . . . . . . . "Symposium: rapid excavation : 5 reports" . "Symposium: Rapid excavation : 5 reports" . . . . . . . . . "National Research Council (U.S.). Highway Research Board. Committee on Soil and Rock Properties." . . "National Research Council (U.S.). Highway Research Board. Annual Meeting" . . "Symposium on Rapid Excavation Procedures (1970 : Washington, D.C.)" . . . "Annual meeting. Highway Research Board (49 1970. Washington, DC)" . . . "Symposium on Rapid Excavation Procedures (1970. Washington, DC)" . . .