Odkazy na procvičování:
http://www.agendaweb.org/vocabulary/numbers-1-20-exercises.html
http://eslgamesworld.com/members/games/vocabulary/memoryaudio/numbers%2010%20to%2020/index.html
https://learnenglishkids.britishcouncil.org/en/word-games/numbers-11-20
http://englishflashgames.blogspot.cz/2011/09/numbers-game.html