1. Experiments on strength of small pillars of coal in the Pitsburgh bed;Greenwald;U.S. Bureau of Mines Technical Paper No. 605,1939
2. Progress report: experiments on strength of small pillars of coal in the Pittsburgh bed;Greenwald;U.S. Bureau of Mines Report, R.I. 3575,1941
3. Rock tests in situ;Nose,1964
4. Measuring the strength of rock in situ at an increasing scale;Jahns,1966
5. A study of the deformation and strength properties of rocks by block tests in situ in iron-ore mines;Gimm,1966