1. A.V. Lourenco, Ann. Chim. Phys, 51 365 (1860);.
2. A.V. Lourenco, Ann. Chim. Phys, 67 293 (1863)
3. P.J. Flory, “Principles of Polymer Chemistry,” Cornell University Press, Ithaca, 1953, pp. 3–28. The nineteenth century research is summarized quite well in this classic text.
4. H. Hlasiwetz and J. Haberman, Ann. Chem. Pharm., 159 304 (1871).
5. H. Pringsheim, Naturwissenschaften, 13 1084 (1925).