1. Chemische Fabrik Griesheim-Elektron (1926).
2. U.S. Patent 1,929,543 (1933).
3. ed., Rubber, Technology, 2nd ed., Van Nostrand Reinhold, N. Y. (1973).
4. Canadian Patent 346,164 (1934).
5. and Chapter 2 in Encyclopedia of PVC, ed., 2nd ed., 2, Marcel Dekker, N. Y. (1988).