1. Wagner H. and Maden B. J. Fifteen years of experience with the design of coal pillars in shallow South African collieries. In Proc. ISRM Symp. Design and Performance of Underground Excavations, Cambridge (Edited by E. T. Brown and J. A. Hudson), pp. 391–399. British Geotechnical Society, London (1984).
2. Rock Mechanics Design in Mining and Tunneling;Bieniawski,1984
3. The effect of specimen size on compressive strength of coal;Bieniawski;Int. J. Rock Mech. Min. Sci.,1968
4. Wagner H. Determination of the complete load–deformation characteristics of coal pillars. In Proc. 3rd ISRM Congr. Advances in Rock Mechanics, Denver, pp. 1076–1081. NAS, Washington, D.C. (1974).
5. Schmidt hammer rebound data for estimation of large scale in situ coal strength (Technical Note);Sheorey;Int. J. Rock Mech. Min. Sci. & Geomech. Abstr.,1984