*[https://www.timexsinclair.com/ Timex Sinclair - The Authoritative Website]
*[https://problemkaputt.de/zxdocs.htm Noca$h's ZXdocs]
*[http://searle.x10host.com/zx80/zx80.html Grant's Sinclair ZX80 Homebuilt hardware]
*[https://oldcomputer.info/8bit/zx81/ULA/ula.htm ZX81 ULA replacement] [[Media:Esquemas ZX81 ULA Andy Rea printable.pdf|ZX81 Project]] [[Media:ZX81 Complete printable.pdf|ZX81 Complete]]
*[https://archive.org/details/TimexSinclairEphemera/Zx81AssemblyManual/mode/2up ZX81 Assembly Instructions]