1. Wackenroder, H. (1831), Mag. Pharm. 33, 144.
2. Berzelius, J. J. (1837), Ann. Pharm. 21, 1837.
3. Guibourt, N. J., Robinet, S. & Derheims, J. (1827), J. Pharm. Chim. 13, 26.
4. Frémy, E. (1860), C. r. Acad. Sci. 50, 405.
5. Stokes, G. G. (1864), J. Chem. Soc. 17, 304.