When searching the MLA Bibiography, generally DO NOT use keywords in the target language, because MLA's indexing is in English-only.
The exception is for the title of a work of literature in its original language.
MLA covers material in many languages. If you want to limit your search to materials written in a particular language, go to the Advanced Search screen. Under the Filters tab, look for the Language limits.
Another method:
After you get some search results, click the All Filters button
then look for the Language option. These filters will reflect what is actually available within your search results.