1. Anon. Available from http://www.msha.gov/s%26hinfo/roofrib/roofrib.htm.
2. Probability concepts in engineering planning and design;Ang,1975
3. Baecher, G.B., 1981. Risk Screening for Civil Facilities. Massachusetts Institute of Technology, Department of Civil Engineering, CER-81-9, 20 pp.
4. Probability statistics and decision for civil engineers;Benjamin,1970
5. Brooks, D.B., Berry, D.R., 1972. Mine health and safety as an analytic problem. Mineral Bulletin 125, Information, Canada, Ottawa.