1. Hörmansdörfer, G., EEC Patent EP 0 402 304 B1, 1996.
2. Bank, D.H., Soukhojak, A.N. and Sehanobish, K., US Patent Application 20120216981, 2012.
3. Kimura Hiroshi and Kai Junjiro, US Patent Application 06/343,767, 1982.
4. Chalk, C.D. and Hayman, C., US Patent 4 619 778.
5. Yamasita Kadzuo, Jpn. Patent 621 161 756, Kakai Tokke Koho, 1989, no. 3(3), pp. 593–594.