Das Referenz allows you to browse Wikipedia in 8 languages: English, German, Spanish, French, Italian, Dutch, Polish and Swedish. We picked these 8 languages because their Wikipedia exceeds a million articles. For each language addition we will have to extend our set of rules for the right typographic treatment. That is why we extend this list very carefully.
The interface of the app (e.g. the button labels) are localized for the English and German language only.
We might add additional Wikipedia languages soon or even extend the localization of the app. Please drop us an email if you think an important language is missing.