1. J.G. Burke, Origins of the Science of Crystals, University of California Press, Berkeley, 1966.
2. G.J. Schneer, Crystal forms and structures, Dowden, Hutchinson and Ross, 1977.
3. A. Bravais, J. ecol. Polytech. 19 (1850) 1.
4. G. Friedel, Bull. Soc. Fr. Miner. Le Couscle Crystallographie, Herman, Paris, 1911.
5. J.D.H. Donnay and D. Harker, Am. Mineral. 22 (1937) 446.