1. Davis, D. H...Jour. of Geo., 1954,62, 1.
2. Fancher, G. H. ..Texas Res. Comm., 1950, Bulletin No. 4.
3. Hughes, D. S. and Cooke, C. E.Geophysics, 1953,18, 2.
4. Tickell, F. G. ..The Examination of Fragmental Rocks.
5. Mechem, O. E. and McCurdy, R. C.Trans. Amer. Inst. Min. Met. Eng., 1933,103, 256.