1. Holland CT. The strength of coal in mine pillars. In: the 6th Symposium on Rock Mechanics, Rolla, MO, USA, 1964, p. 450–6.
2. Strength and stability of pillars in coal mines;Steart;J Metall Min Soc S Afr,1954
3. A study of the ultimate strength of coal as related to the absolute size of the cubical samples tested;Gaddy,1956
4. Evans I, Pomeroy CD. The strength of cubes of coal in uniaxial compression. In: mechanical properties of non-metallic and brittle materials, London, Butterworth Scientific Publications, 1958, p. 5-28.
5. The effect of specimen size on compressive strength of coal;Bieniawski;Int J Rock Mech Min Sci,1968