ZX81
- http://www.scribd.com/doc/56780765/ZX81Assembly
- http://www.users.waitrose.com/~thunor/mmcoyzx81/index.html
- http://www.worldofspectrum.org/ZX81BasicProgramming/
- http://www.larwe.com/museum/download/ts1000_instructions_lowres.pdf
- http://www.zx81kit.com/online_zx81_manual.htm
- http://zx81stuff.org.uk
- http://www.zx81museum.net