"Liebig-Denkmünze". chemie.de (in German). 14 December 2012. Retrieved 15 September 2020.
chemistryworld.com
Sella, Andrea. "Schott's glass". chemistryworld.com. Royal Society of Chemistry. Retrieved 20 December 2020.
doi.org
Kurkjian, Charles R.; Prindle, William R. (1998). "Perspectives on the History of Glass Composition". Journal of the American Ceramic Society. 81 (4): 795–813. doi:10.1111/j.1151-2916.1998.tb02415.x.