1. Bradley, W. F. and Grim, R. E.Am. Min., 1951,36, 182–201.
2. Grim, R. E. and Rowland, R. A. Ibid., 1942,27, 801–18.
3. Hess, H. H., Smith, R. J. and Dengo, G. Ibid., 1952,37, 68–75.
4. Kulp, J. L., Kent, P. and Kerr, P. F. Ibid., 1951,36, 643–670.
5. Nagy, B...Ec. Geol., 1953,48, 591–97.