1. Baecher, G. B., Lanney, N. A., Einstein, H. H. (1977): Statistical Description of Rock Properties and Sampling. Proc. 18th U. S. Symp. on Rock Mech., Colorado, 5c1.1?5c1.8.
2. Bridges, M. C., (1976): Presentation of Fracture Data for Rock Mechanics. Proc. 2nd Australia-New Zealand Conference on Geomechanics, 144?148.
3. Condit, D. D. (1912): Conemaugh Formation in Ohio. Bulletin 17, 4th Series, Geologic Survey of Ohio, Columbus, Ohio.
4. Glynn, E. F., Veneziano, D., Einstein, H. H. (1978): Probabilistic Model for Shearing Resistance of Jointed Rock. Proc. 19th U. S. Symp. on Rock Mech.
5. Robertson, A. MacG. (1970): The Interpretation of Geological Factors for Use in Slope Theory. In Planning Open Pit Mines (Van Rensburg, P. W. J., Ed.). Cape Town, South Africa: Balkema.