: The .doi file is a proprietary data format that contains the compressed audio, text, and subtitle assets for a specific language (in this case, English/angielski).

: To ensure a game installs in English, the angielski.doi file must be placed in the same folder as the setup.exe before running the installer. Potential Confusion with DOI (Digital Object Identifier)

: In many Polish academic reports, "j. angielski, DOI: [link]" simply indicates that a publication is in the English language and provides its unique scholarly identifier. Features of the DOI registrar – Crossref