*[https://www.timexsinclair.com/ Timex Sinclair - The Authoritative Website]
*[https://problemkaputt.de/zxdocs.htm Noca$h's ZXdocs]
*[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]
*[https://youtu.be/1Jr7Q1yJOUM Documentary - The Sinclair ZX80, ZX81, and Timex Sinclair 1000] by [[The 8-Bit Guy]]
*[https://youtu.be/spxAQkTzvDQ Sinclair ZX81 (Timex 1000) Grandaddy of Computers] by [[Nostalgia Nerd]]