P.S. Gaskell; P.A. Ratliff (February 1977). "QUADRAPHONY: developments in Matrix H decoding"(PDF). Research Department, Engineering Division. BBC. BBC RD 1977/2. Archived(PDF) from the original on October 2, 2009. Retrieved August 13, 2018.
decoy.iki.fi
P.S. Gaskell; P.A. Ratliff (February 1977). "QUADRAPHONY: developments in Matrix H decoding"(PDF). Research Department, Engineering Division. BBC. BBC RD 1977/2. Archived(PDF) from the original on October 2, 2009. Retrieved August 13, 2018.