Would it be an advantage for a committed modern day research mathematicians to learn any foreign language? Are there works in Russian, French, or any other foreign language being produced or that have not been translated?
closed as primarily opinion-based by Daniel W. Farlow, Mark Fantini, user147263, Hagen von Eitzen, Lee Mosher Apr 4 '15 at 21:39
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Yes, there are many such works. These days, less French than Russian, but still a decent chunk of both.
Would it be an advantage for a committed modern day research mathematicians to learn any foreign language?
Knowing other languages and cultures (other than your native one) can make one a more interesting person which will certainly help during the job search phase and in general academic life.
For a lot of algebraic stuff you'll need at least a little French. Note that being good enough at a language to read a math paper with the aid of a dictionary is wildly less than the amount you need to have a conversation, so it's not asking too much for someone to pick up this ability in a few languages. Just sit down and practice through some papers where you're already comfortable with the math (say, a textbook in a subject you know very well) and you will be fine, although it will take some patience and hopefully a friend who speaks the language well.