1. Sosman, R. B. “The Properties of Silica” (American Chemical Society), 1927, Chaps.20, 386–87;34, 671–97.
2. Micheli, F. J.Arch. Phys. Nat., 1902, (4)13, 217.Ann. d. Physik., 1902, (4)7, 772.
3. Rinne, F., and Kolb, R.Neues. Jarb. Min., 1910,II, 138.
4. Reimerdes, E.Inaug. Dissert. Jena, 1896,39, 14.
5. Ramachandran, G. N.Proc. Ind. Acad. Sci., 1946,25, 266–375.