1. Barton N, Lien R, Lunde J (1974) Engineering classification of rock masses for the design of tunnel support. Rock Mech 6:183–236
2. Bieniawsky ZT (1973) Engineering classification of jointed rock masses. Trans S Afr Inst Civ Eng 15:335–344
3. Bieniawsky ZT (1989) Engineering rock mass classification: a complete manual for engineers and geologists in mining, civil and petroleum engineering. Wiley-Interscience publication, New York
4. Deere DU, Hendron AJ, Patton FD, Cording EJ (1967) Design of surface and near surface construction in rock. In: proceedings of 8th US symposium Rock Mechanics, AIME, New York, pp 237–302
5. Gonzalez de Vallejo LI (1983) A new rock classification system for underground assessment using surface data. In: Proceedings of International Symposium Engineering Geology Underground Construction, LNEC, Lisbon, vol. 1, pp II.85–II.94