Posso, Patrick. "Minicassette for Recording Tape." U.S. Patent number 3934842. Washington DC: United States Patent and Trademark Office, 1973. http://www.uspto.gov/patft/index.html (25 March 2008).

Posso, Patrick. "Minicassette for Recording Tape." U.S. Patent number 3934842. Washington DC: United States Patent and Trademark Office, 1973. http://www.uspto.gov/patft/index.html (25 March 2008).