1. Recording drilling performance for tunneling site investigations;Brown;Rept to CIRIA (U.K.), Technical Note no. 81,1977
2. Drillability studies—impregnated diamond bits;Paone;USBM RI 6776,1966
3. Machine boring and the mechanical properties of hard rock;Handewith,1970
4. Hard rock tunnelling system evaluation and computer simulation;Hibbard;General Res. Corp. (Arlington, U.S.A.), Rept no. HO/11 0238,1971
5. Tunnelling with machines working on the undercutting principle;Barendsen,1970