File:Vintage Hewlett-Packard Model HP-45 Advanced Scientific Pocket Calculator, HP's Third Handheld Electronic Calculator, Introduced in 1973 and Discontinued in 1976 (38772251491).jpg - Wikimedia Commons
Restoring my Grandfathers HP-45 - Vintage Calculator Returned to Life - YouTube
HP-65 - First programmable Pocket Calculator | Pocket calculators, Calculator, Computer history