1. US 4.193.942 (1980) and US 4.292.198 (1981) both from Stamicarbon; US 5.936.049 (1999 Mitsui); US 5.935.892 (2000 CIT); EP 0.040.891 (1984 Stamicarbon); Pignataro; Börner/Franke; Horváth Vol. 4 p.185;
2. Volkov p.114;
3. Cornils/Herrmann‐5 p.297;
4. McKetta‐1 Vol. 51 p.435;