1. Harris, Stephen J., WO Patent 95-IE8 19950124, 1995.
2. Hwang, Kou M.; Ki, You M.; Liu, Su Ying; Lee, T. C.; Choy, W.; Chen, J. WO Patent 9403165, 1985.
3. Hwang, Kou M.; Ki, You M.; Liu, Su Ying; Choy, W.; Chen, J. (Genelab Technologies, Inc. USA) WO Patent 9403164, 1984.
4. Hulmes, D.; Coleman, A.; Aubert-Foucher, E. (CNRS, Fr) WO patent 0007585, 2000.