1. Ullmann's Encyclopedia of Industrial Chemistry, 7th ed., Electronic Release, Wiley-VCH, Weinheim 2003.
2. K. Weissermel, H.-J. Arpe, Industrielle Organische Chemie, 5th ed., Wiley-VCH, 1998, 326;
3. http://pep.sric.sri.com/Public/Reports/Phase_86/RW86-2-1/RW86-2-1.html.
4. (Degussa), German Patent DE 888691, 1952.
5. T. H. Vanderspurt (Celanese Corp.), Offenlegungsschrift 2734811, 1978.