1. a ICI, British Patent, 1175666 (1966), 1392037 (1971), 1446069 (1973), 1489406 (1974), 1166998 (1965)
2. b ICI, GFR Patent, 2714739 (1977), 2813980 (1978), 2714204 (1977), 2549450 (1976)
3. c Bayer, GFR Patent, 2526172 (1976), 2536490 (1977), 2556489 (1977), 2158924 (1971), 2740824 (1979), 2430682 (1976), 1644600 (1966)
4. d Bayer, British Patent, 1454475 (1974), 1430899 (1973), 1457231 (1974), 1461058 (1974), 1434462 (1973)
5. e PŁ, Polish Patent, 61945 (1967)