1. Stompel, Z., Collin, G., Szen, A. and Herion, G. Koks Smoia Gaz. (1989), 33, 24.
2. Alama,K., Collin,G. et al. Drogownictwo. (1987), 415, 75.
3. Herion, G. and Sybilski, D. Erdiil Kohle, Erdgas, Petrochem. 1991, 44, 357.
4. Pol. Pat. 158 812, 1988; Ger. Pat. 3 919 209, (1988).
5. Franck, Heinz G.; Metzendorf, Walter; Schweym, Erich. et al. US Pat 3784487, (1974).