Billi, R.; Canavesio, F.; Ciaramella, A.; Nebbia, L. (1995). "Interactive voice technology at work: The CSELT experience". Speech Communication. 17 (3–4): 263–271. doi:10.1016/0167-6393(95)00030-R.
espacenet.com
worldwide.espacenet.com
Cavazza, Michele, and Alberto Ciaramella. "Device for speaker's verification." U.S. Patent No. 4,752,958. 21 June 1988. (the IT patent was submitted in 1983, see it in Espacenet)