1. F.G. Young, J.T. Fitzpatrick, US patent 2,580,714, assigned to Union Carbide, (January 1, 1952).
2. C. Matasa, A. Cocan, E. Tonca, Romanian Patent 51482, (January 25, 1969).
3. J.D. Holmes, H.J. Hagemeyer, Jr., US patent 3,915,995, assigned to Eastman Kodak Company, (October 28, 1975).
4. Vses Nauchn Konf Khim Tekhnol Furanovykh Soedin, Tezisy Dokl;Osis,1978
5. C.D. Chang, P.D. Perkins, US patent 4,388,461, assigned to Mobil Oil Corp., (June 14, 1983).