1. https://zpravy.aktualne.cz/ekonomika/prukaz-isic-nabizi-studentum-slevy-uz-sedesat-let/r~d15d6ce412ce11e387940025900fea04/?redirected=1546807749
2. https://www.isic.org/about-us/history/
3. https://www.zelenypruh.cz/isic
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