Literature survey in multiple languages The following question has been induced by a comment to the question What to do if chosen topic has been done in a foreign language.

I know four languages (+-1) sufficiently well to be able to read and comprehend literature specific to my field (math/phys). When doing a literature survey before starting the research phase for my thesis (masters now, phd later) should I look for literature in all the languages I comprehend or would only two (i.e., EN/DE or EN/RU) suffice?

Specifically for masters a check in all the languages seems like an overkill to me, given the limited amount of time available.
I would not do a multi-language literature search for Master's degree (due to limited time, as you mentioned, plus simply because expectations for a Master's level of research are significantly lower than the one of Ph.D. level. Having said that, I've seen some pretty solid research-focused Master's theses, but they are relatively rare.

On the other hand, performing a multi-language literature review for a Ph.D. research seems like a good idea, as it would allow you to cover the topic as well as related fields of study and research streams much more comprehensively (in both width and depth), which is an expectation for a doctoral-level research. However, you should always be focused on your main goals and assess your literature search with overall Ph.D. program's and dissertation's time frames in mind. It is so very easy to get addicted to exploring vast volumes of existing research, even restricting yourself to a particular subject domain. That introduces the risk of spending way too much time on that, jeopardizing other essential parts of your research study. You have been warned! And good luck!