Slide calculator - Wikipedia

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The invention that altered history: The slide rule - The Jerusalem Post

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Calculator - Wikipedia

File:Vintage Rockwell Scientific Slide Rule Electronic Pocket Calculator, Model 63R, Rechargeable Battery & AC Adapter, Assembled In Mexico, Circa 1975 (39863857230).jpg - Wikimedia Commons

File:Slide Rule-Karoly Szabo.jpg - Simple English Wikipedia, the free encyclopedia

File:Vintage Sears Electronic Slide Rule II Pocket Calculator, Model 801.58780, Blue Fluorescent Display, Made In Mexico, Circa 1974 (15102583297).jpg - Wikimedia Commons

Slide rule - Wikipedia

Mic-UK: A gallery of a selection of calculating aid designs spanning over 2000 years.

Calculator - Wikipedia