File:Vintage Radio Shack Blackjack 21 Combination Blackjack and Electronic Pocket Calculator, Model EC-21, Catalog No. 60-3011, Made in Taiwan (12109795754).jpg - Wikimedia Commons
Unlimited Blackjack - Wizard of Odds
Blackjack Strategy Calculator - Bovada Casino Online Blog
Eddie's Math and Calculator Blog: Retro Review: Radio Shack EC-21 (Blackjack Calculator)
Basic Strategy for European Blackjack - charts - Wizard of Odds
Blackjack Calculator - Best Blackjack Strategy Trainer - Blackjack.org
GitHub - alessiomeloni/blackjack-strategy-calculator: This blackjack coach will provide you with the optimal move based on your cards and the dealer's cards, using the Hi-Lo system, Betting Deviations, and Playing Deviations strategies.