The Gateway Guide to the ZX81 and ZX80 More Than 70 Programs: Mark Charlton: 9780916688271: Amazon.com: Books
Machine Language Programming Made Simple for your Sinclair & Timex TS1000 (Retro Reproductions): Beam Software: 9781789829662: Amazon.com: Books
The Sinclair ZX81 – and six of the best ZX81 games | Stuff
Not Only 30 Programs for the Sinclair ZX81 (Retro Reproductions): Retro Reproductions: 9781837910205: Amazon.com: Books
Sinclair ZX81 System Story - Nostalgia Nerd
The Century computer programming course: The complete guide to programming in Sinclair BASIC using the ZX81 and Spectrum microcomputers: Peter Morse: 9780712600736: Amazon.com: Books