1. US 9.266.990 (2016); US 9.149.968 and 8.440.300 (2013/2015 BASF); US 5.866.670 (1999 Polyplastics); Ullmann Vol.A21 p.591;
2. Mark/Bikales/Overberger/Menges Vol. 11 p.286;
3. Polymerization of Formaldehyde Using Tetravalent Organo-Tin Compounds as an Initiator