* http://www.kjthacker.f2s.com/docs/audiocd2.html - DIY - '''caution:''' the disclaimer on that webpage says that it is '''not''' based on the real Codemasters CD - so it may be totally incompatible to the original Codemasters CD (?)
* http://worldofspectrum.org/ - has a review about the Spectrum version - which conflicts with the DIY info (the Spectrum review implies it contains a mono 1-bit A/D converter, not a stereo connection without A/D converter) (the A/D converter - if it does exist - might refer to something simple, like a transistor)
* http://www.olivertwins.com/ - according to this webpage, the Oliver Twins created "The CD Games Pack" in December 1989, for Amstrad CPC, Spectrum, and Commodore 64, published by Codemasters