Oh, my favourite format during my undergraduate time!
Most books in mathematics and physics (some old and niche) were available in the "Russian library".
At the same time, I haven't yet seen DjVu used in a legit way.
At the same time, I haven't yet seen DjVu used in a legit way.
(Not so fun fact: if you punch "filetype:djvu" into Google right now, you can easily page through what supposedly is every DjVu file on the Internet as far as Google knows, which is not many: "In order to show you the most relevant results, we have omitted some entries very similar to the 300 already displayed." I learned this the hard way when I began wondering why a bunch of DjVu fulltexts I hosted never seemed to show up in Google or Google Scholar...)