Slide calculator - Wikipedia

HP-35 - Wikipedia

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

HP calculators - Wikipedia

Pascal's calculator - Wikipedia

Calculator - Wikipedia

Ezyaid Pregnancy Wheel, OB-GYN Due Date Calculator, Gestational EDC Wheel for Midwives and Health Workers : Health & Household

E6B - Wikipedia

File:BLW Mechanical Calculator (1).jpg - Wikipedia

TI SR-50 - Wikipedia

Calculator - Wikipedia

The Slide Rule: A Computing Device That Put A Man On The Moon : NPR Ed : NPR